Method for producing cellulose acylate composition and cellulose acylate film

ABSTRACT

A method for producing a cellulose acylate composition, which comprises filtering a solution in which cellulose acylate satisfying the following formulae 1 to 3 and having melt viscosity of 150 to 1000 Pa·s at 230° C. is dissolved in a solvent through a filter having a retention particle size of 0.1 to 40 μm, and mixing the filtered solution with a poor solvent to reprecipitate cellulose acylate:
 
1.5≦ A+B ≦3  Formula 1
 
0≦A≦2.0  Formula 2
 
1.0≦B≦3  Formula 3
 
where A is a substitution degree for an acetyl group of a hydrogen atom which constitutes a hydroxyl group of cellulose, and B is a substitution degree for an acyl group having 3 to 7 carbon atoms of a hydrogen atom which constitutes a hydroxyl group of cellulose.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cellulose acylate composition whichcontains a very small amount of fine impurity and is useful for anoptical film, and a method for producing the same. Furthermore, theinvention pertains to a high grade optical film, a retardation film, apolarizing plate, an optical compensation film, an anti-reflection film,and an image display device employing the above-mentioned celluloseacylate.

2. Description of the Related Art

Due to the transparency, toughness, and optical isotropy, celluloseacetate is increasingly finding its usefulness in a variety ofapplications, including the use in the support of photographic sensitivematerials, as well as the use in optical films for image display devicesincluding liquid crystal display devices and organic EL display devices.With regard to the optical film for liquid crystal display devices,methods of using cellulose acetate for polarizing plate protectivefilms, or for retardation films for liquid crystal display devices ofSTN (Super Twisted Nematic) mode or the like by stretching the film toattain in-plane retardation (Re) and retardation in the thicknessdirection (Rth), are being implemented.

In recent years, there have been developed display devices of VA(Vertical Alignment) mode, OCB (Optical Compensated Bend) mode, or IPS(In-Plane Switching) mode, where higher values of retardation such as Reand Rth are required compared with the STN mode. Thus, an optical filmmaterial having property of manifesting various types of retardationaccording to the type of liquid crystal mode is on demand.

Stretchability of cellulose acetate is poor, and an area whereretardation due to stretching and alignment of only polymer is realizedis limited. Furthermore, since cellulose acetate is a relativelyhydrophilic polymer, a change in retardation caused by humidity issignificant.

In order to cope with such demand, a cellulose acylate film has beendisclosed as a new material for optical film, which is produced by asolution casting method in which a solution of mixed esters of an acetylgroup and a propionyl group of cellulose (mixed acylate of cellulosesuch as cellulose acetate propionate) is flow cast on a support, aportion of the solvent is evaporated, and then a cellulose acylate filmis peeled off from the support (see JP-A-2001-188128). In addition,there is a process in which cellulose acetate butyrate and celluloseacetate propionate are used as mixed acylate of cellulose that has amelting temperature lower than that of cellulose acetate and then meltcast to form an optical film (see JP-A-2000-352620). The melt castinghas the following advantages. Since an organic solvent is not usedduring the casting, a dissolution or dry process may be omitted unlikethe solution casting, and a load to environment is low.

Mixed acylate of cellulose such as cellulose acetate propionate andcellulose acetate butyrate is an excellent material that increasesretardation of cellulose acetate. Meanwhile, in the case of when aprocess where cellulose and acid anhydrides that are industriallyavailable are reacted in the presence of an acid catalyst to producecellulose acylate is used, reactivity is lower as compared to celluloseacetate, impurities including unreacted cellulose may easily remain. Theimpurities are observed as black point impurities or bright pointimpurities under a crossed Nicols condition. In the case of whencellulose acylate is used as an optical film, optical defects may beformed or light leakage may occur, thus it is required that the amountof impurities is set to be very small.

An activation process in which an acetic acid is added to raw materialcellulose and a temperature is maintained at 40° C. for 1 hour or moreis disclosed as a process of reducing unreacted cellulose of mixedacylate of cellulose (see JP-A-2006-45500).

This process is useful to reduce the amount of unreacted substanceswhile the degree of polymerization of cellulose acylate is maintained ata relatively high level. However, it is difficult to remove impuritiesother than unreacted cellulose, and when the required amount ofunreacted substance is very small, it is necessary to perform a processof removing the impurities.

In the case of when cellulose acylate is used as a raw material of theoptical film, if the casting process is the solution casting process,even though cellulose acylate containing a large amount of impurity isused, a cellulose acylate solution is prepared, filtered by using afilter having a small retention particle size, and cast to significantlyreduce the amount of impurity of products (see JP-A-2003-213004).

Furthermore, a process of filtering melts of cellulose ester in the caseof when the melt casting is performed is disclosed. In the process,desirable filtration precision is 5 μm or less (see JP-A-2000-352620).However, there is a problem in that replacement of a filtering materialduring the filtration of the melts is more difficult as compared to thefiltration of the solution.

Therefore, in order to produce cellulose acylate useful to provideacceptable optical properties when the melt casting is performed, it isrequired that the amount of fine impurity contained in the raw materialof cellulose acylate used to perform the melting is set to be very smallto make the filtration of melts unnecessary. However, this is difficultto be achieved by using a known method, thus there is a need to providea method of solving this problem.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for producingcellulose acylate composition which contains a very small amount of fineimpurity and is useful for an optical film. It is another object of theinvention to provide a high grade optical film, a retardation film, apolarizing plate, an optical compensation film, an anti-reflection film,and an image display device employing the above-mentioned celluloseacylate.

In order to obtain an acceptable optical film, it is required that theamount of impurity having a retention particle size of 40 μm or more isset to 0.1 or less pieces of particles per 1 g of the cellulose acylatecomposition. However, it has been considered that it is industriallyimpossible to remove the impurity having a retention particle size of 40μm or more from the melts so that the amount of the impurity is in theabove-mentioned range.

Accordingly, the present inventors have devotedly conducted researches,and as a result, these found that when cellulose acylate constituting acellulose acylate composition which satisfies Formulae 1 to 3 and has amelt viscosity of 150 to 1000 Pa·s at 230° C. is dissolved in a solventto form a solution and the solution is filtered by using a filter havinga retention particle size of 0.1 to 40 μm and mixed with a poor solventto reprecipitate cellulose acylate, cellulose acylate is useful to amelt casting process to appropriately remove the impurity and preventfragileness of the film from being made worse, thereby accomplishing theinvention.

The above-mentioned objects of the invention are achieved by thefollowing aspects of the invention.

(1) A method for producing a cellulose acylate composition, whichcomprises filtering a solution in which cellulose acylate satisfying thefollowing formulae 1 to 3 and having melt viscosity of 150 to 1000 Pa·sat 230° C. is dissolved in a solvent through a filter having a retentionparticle size of 0.1 to 40 μm, and mixing the filtered solution with apoor solvent to reprecipitate cellulose acylate:1.5≦A+B≦3  Formula 10≦A≦2.0  Formula 21.0≦B≦3  Formula 3where A is a substitution degree for an acetyl group of a hydrogen atomwhich constitutes a hydroxyl group of cellulose, and B is a substitutiondegree for an acyl group having 3 to 7 carbon atoms of a hydrogen atomwhich constitutes a hydroxyl group of cellulose.(2) The method for producing the cellulose acylate composition accordingto (1), wherein the cellulose acylate used in the solution has a weightaverage molecular weight measured by a gel permeation chromatography of80,000 to 180,000.(3) The method for producing the cellulose acylate composition accordingto (1) or (2), wherein the filter has a retention particle size of 2 to20 μm.(4) The method for producing the cellulose acylate composition accordingto any one of (1) to (3), wherein a filter aid is used during thefiltering.(5) The method for producing the cellulose acylate composition accordingto any one of (1) to (4), wherein the reprecipitated cellulose acylatecomprises 10 pieces or less of impurity particles having a particle sizeof 40 μm or more per 100 g of the cellulose acylate.(6) The method for producing the cellulose acylate composition accordingto any one of (1) to (4), wherein the reprecipitated cellulose acylatecomprises 5 pieces or less of impurity particles having a particle sizeof 40 μm or more per 100 g of the cellulose acylate.(7) The method for producing the cellulose acylate composition accordingto any one of (1) to (6), wherein the cellulose acylate composition isin the form of a solution, a melt, a gel, a pellet, or a film.(8) The method for producing the cellulose acylate composition accordingto any one of (1) to (6), wherein the cellulose acylate composition isin the form of a pellet or a film.(9) A cellulose acylate film produced by the method for producing thecellulose acylate composition according to any one of (1) to (8).(10) The cellulose acylate film according to (9), wherein the amount ofremaining organic solvent is 0.03% by mass or less.(11) The cellulose acylate film according to (9) or (10), which has anin-plane retardation (Re) satisfying the following formula i and aretardation in the thickness direction (Rth) satisfying the followingformula ii:−500 nm≦Re≦500 nm  Formula i−500 nm≦Rth≦500 nm.  Formula ii(12) The cellulose acylate film according to any one of (9) to (11),which is obtained by stretching the cellulose acylate film according toclaim 9 in at least one direction by 0.1 to 500%.(13) A retardation film comprising the cellulose acylate film accordingto any one of (9) to (12).(14) A polarizing plate comprising a polarizing layer and a protectivefilm provided on at least one side of the polarizing layer, wherein theprotective film is the cellulose acylate film according to any one of(9) to (12) or the retardation film according to (13).(15) An optical compensation film comprising an optically anisotropiclayer formed by aligning a liquid crystalline compound on the celluloseacylate film according to any one of (9) to (12) or the retardation filmaccording to (13).(16) An anti-reflection film comprising an anti-reflection layer on thecellulose acylate film according to any one of (9) to (12) or theretardation film according to (13).(17) An image display device comprising one or more selected from thegroup consisting of the cellulose acylate film according to any one of(9) to (12), the retardation film according to (13), the polarizingplate according to (14), the optical compensation film according to(15), and the anti-reflection film according to (16).

BEST MODE FOR CARRYING OUT THE INVENTION

A cellulose acylate composition according to a production method of theinvention contains a very small amount of fine impurity and is usefulfor an optical film, particularly, an optical film using a melt castingprocess. Furthermore, a high grade optical film, a retardation film, apolarizing plate, an optical compensation film, an anti-reflection film,and an image display device employing the above-mentioned celluloseacylate are of good quality and have excellent optical properties.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a cellulose acylate composition and a method for producingthe same according to an aspect of the invention will be described indetail. The explanation of the constitutional requirements describedbelow is based on the representative embodiments of the invention, butthe invention is not intended to be limited by those embodiments. Inaddition, the numerical value range expressed with symbol “ . . . to . .. ” in the present specification implies that the range includes thevalues described before and after the symbol “ . . . to . . . ” as thelower limit value and the upper limit value.

<Cellulose Acylate>

A detailed description will be given of cellulose acylate which ispreferably used in the method according to the aspect of the invention.

(Basic Structure)

The β-1,4-bonded glucose unit constituting the cellulose has freehydroxyl groups at the 2-position, 3-position, and 6-position. Celluloseacylate is a polymerized product (polymer) having part or all of thehydroxyl groups that are chemically-modified. In the aspect of theinvention, the term “substitution degree” indicates the sum of theratios at which the hydroxyl groups of cellulose are substituted inrespect to the 2-position, 3-position, and 6-position (for example,esterification of 100% means that the degree substitution is 1).Furthermore, a natural cellulose raw material may contain a polymer(hemicellulose) of sugars (for example, xylose, mannose, or the like)other than glucose or components other than cellulose, for example,lignin, according to the type of its original living things orpurification process. However, in the aspect of the invention, a polymerthat is produced by using the cellulose raw material containing them isdescribed generically as cellulose acylate.

The cellulose acylate according to the aspect of the invention satisfiesthe following formulae 1 to 3:1.5≦A+B≦3  Formula 10≦A≦2.0  Formula 21.0≦B≦3  Formula 3

In formulae, A represents a substitution degree for an acetyl group inrespect to a hydrogen atom that constitutes a hydroxyl group ofcellulose, and B represents a substitution degree for an acyl grouphaving 3 to 7 carbon atoms in respect to a hydrogen atom thatconstitutes a hydroxyl group of cellulose.

(Substituent Designated by B)

In the aspect of the invention, the substituent that is designated by Bhas preferably 11 carbon atoms or less, more preferably 3 to 6 carbonatoms, and particularly preferably 3 or 4 carbon atoms. If the number ofcarbon atoms is set to 11 or less, processability is apt to be improved.If cellulose acylate is used for films, a glass transition temperatureof the polymer is more preferable.

Preferable examples of the substituent may include a propionyl group, abutyryl group, a pentanoyl group, a heptanoyl group, a hexanoyl group,an isobutyryl group, a pivaloyl group, and the like. More preferred area propionyl group, a butyryl group, a hexanoyl group, and most preferredare a propionyl group and a butyryl group.

It is preferable that the cellulose acylate according to the aspect ofthe invention satisfy the following formulae 4 to 6:2.0≦A+B≦3  Formula 40.05≦A≦2.0  Formula 51.0≦B≦2.95  Formula 6

It is more preferable that the cellulose acylate according to the aspectof the invention satisfy the following Formulae 7 to 9:2.5≦A+B≦2.99  Formula 70.1≦A≦1.5  Formula 81.2≦B≦2.9  Formula 9

It is most preferable that the cellulose acylate according to the aspectof the invention satisfy the following Formulae 10 to 12:2.6≦A+B≦2.98  Formula 110.1≦A≦1.2  Formula 121.3≦B≦2.85  Formula 13

In the case of when A+B is less than 1.5, hydrophilicity of celluloseacylate excessively increases, resulting in increased humiditydependency of the cellulose acylate composition, and thus it is notdesirable. In the case of when A+B is 2.0 or more, since it is possibleto obtain an optical film having acceptable humidity dependency, it isdesirable. In the aspect of the invention, A+B is preferably 2.5 ormore, more preferably 2.6 or more, and particularly preferably 2.7 ormore.

A may have any value in the range of 0 to 2. In the case of when thecellulose acylate composition according to the aspect of the inventionis a film, A is preferably 0.05 or more, more preferably 0.1 or more,and particularly preferably 0.2 or more in order to obtain desirableoptical properties. As to the upper limit thereof, A is preferably 1.5or less and more preferably 1.2 or less in views of cost, the shape ofthe film surface, and the like.

B may have any value in the range of 1 to 3. In the case of when thecellulose acylate composition according to the aspect of the inventionis a film, B is preferably 1.0 or more, more preferably 1.2 or more, andparticularly preferably 1.3 or more in order to obtain desirable opticalproperties, mechanical properties, and castability. As to the upperlimit thereof, B is preferably 2.95 or less, more preferably 2.9 orless, and particularly preferably 2.85 or less in views of opticalproperties and processability.

Preferable examples of cellulose acylate that is used in the aspect ofthe invention may include cellulose acetate propionate, celluloseacetate butyrate, cellulose acetate heptanoate, cellulose acetatehexanoate, and cellulose acetate pentanoate. More preferable arecellulose acetate propionate, cellulose acetate butyrate, celluloseacetate heptanoate, and cellulose acetate hexanoate. Most preferable arecellulose acetate propionate and cellulose acetate butyrate.

<Method for Producing Cellulose Acylate>

(Raw Material and Pretreatment)

For the cellulose raw material, materials derived from hardwood pulp,softwood pulp, and cotton linter are preferably used. For the celluloseraw material, materials of high purity having a α-cellulose content of92 to 99.9% by mass are preferably used.

When the cellulose raw material is in a sheet form or in a lump form,the material is preferably pulverized in advance, and the cellulose ispreferably continued to be pulverized until a fluffy state, a featherstate, or a power state is attained.

(Activation Process)

In the aspect of the invention, the cellulose raw material is preferablysubjected to a pretreatment (activation) of coming into contact with anactivating agent, prior to etherification. In the case of whenetherification is performed, water or a sodium hydroxide aqueoussolution is preferably used as an activating agent. In the case of whenesterification is performed, a carboxylic acid is preferably used. Themethod of addition can be selected from methods of spraying, dropping,immersion, and the like, and the activation may be performed at apredetermined temperature for a predetermined time. Details of theactivation treatment are disclosed in JP-A-2006-45500.

(Acylation Process)

In order to produce cellulose acylate according to the aspect of theinvention, cellulose is preferably acylated in the presence of catalyst.Specifically, it is preferable to acylate the hydroxyl group ofcellulose by adding a carboxylic acid anhydride to cellulose andreacting them in the presence of a Brønsted acid or Lewis acid as thecatalyst. For the catalyst, a sulfuric acid can be favorably used. Thesynthesis of cellulose acylate having the large substitution degree at6-position is disclosed in JP-A-1999-5851, JP-A-2002-212338,JP-A-2002-338601, or the like.

(Acid Anhydride)

The acid anhydride of carboxylic acid is preferably an acid anhydride ofa carboxylic acid having 2 to 7 carbon atoms, and examples thereof mayinclude anhydrous acetic acid, propionic acid anhydride, butyric acidanhydride, 2-methylpropionic acid anhydride, valeric acid anhydride,3-methylbutyric acid anhydride, 2-methylbutyric acid anhydride,2,2-dimethylpropionic acid anhydride (pivalic acid anhydride), hexanoicacid anhydride, 2-methylvaleric acid anhydride, 3-methylvaleric acidanhydride, 4-methylvaleric acid anhydride, 2,2-dimethylbutyric acidanhydride, 2,3-dimethylbutyric acid anhydride, 3,3-dimethylbutyric acidanhydride, cyclopentanecarboxylic acid anhydride, heptanoic acidanhydride, cyclohexanecarboxylic acid anhydride, benzoic acid anhydride,and the like. More preferred ones are anhydrous acetic acid, propionicacid anhydride, butyric acid anhydride, valeric acid anhydride, hexanoicacid anhydride, and heptanoic acid anhydride, and particularly preferredones are anhydrous acetic acid, propionic acid anhydride, and butyricacid anhydride.

For the method of obtaining a mixed acylate of cellulose, it ispreferable to use these acid anhydrides in combination. The mixing ratiois preferably determined in accordance with the rate of substitution ofthe target mixed ester. The acid anhydride is usually added in anequivalent excess with respect to the cellulose. That is, the acidanhydride is preferably added in an amount of 1.1 to 50 equivalents,more preferably 1.2 to 30 equivalents, and particularly preferably 1.3to 10 equivalents, with respect to the hydroxyl group of the cellulose.

For a mixed acylation method, mention may be made of a method of mixingor sequentially adding two types of carboxylic acid anhydrides andallowing them to react, a method of using a mixed acid anhydride of twotypes of carboxylic acids (for example, mixed acid anhydride of anacetic acid and a butyric acid), and a method of using acid anhydridesof a carboxylic acid and a different carboxylic acid (for example,acetic acid anhydride and butyric acid anhydride) as the startingmaterials to synthesize a mixed acid anhydride (for example, mixed acidanhydride of an acetic acid and a butyric acid) in the reaction systemand reacting the mixed acid anhydride with cellulose.

(Catalyst)

For the catalyst for acylation used for the production of the celluloseacylate according to the aspect of the invention, it is preferable touse a Brønsted acid or a Lewis acid. The definitions for the Brønstedacid and the Lewis acid are described in, for example, “Encyclopedia ofPhysics and Chemistry”, Vol. 5 (2000). Preferred examples of theBrønsted acid may include a sulfuric acid, a perchloric acid, aphosphoric acid, a methanesulfonic acid, a benzenesulfonic acid, ap-toluenesulfonic acid, and the like. Preferred examples of the Lewisacid may include zinc chloride, tin chloride, antimony chloride,magnesium chloride, and the like.

For the catalyst, the sulfuric acid or the perchloric acid is morepreferred, and the sulfuric acid is particularly preferred. It ispreferable to use the sulfuric acid and other catalysts in combination.A preferred amount of addition for the catalyst is 0.1 to 30% by mass,more preferably 1 to 15% by mass, and particularly preferably 3 to 12%by mass, with respect to the cellulose.

(Solvent)

In carrying out the acylation, a solvent may be added for the purpose ofadjusting the viscosity, rate of reaction, stirrability, ratio of acylsubstitution, or the like. For the solvent, dichloromethane, chloroform,carboxylic acid, acetone, ethyl methyl ketone, toluene,dimethylsulfoxide, sulfolane, or the like may be used, but preferablyused are carboxylic acids. Examples of such carboxylic acid may includea carboxylic acid having 2 to 7 carbon atoms (for example, an aceticacid, a propionic acid, a butyric acid, a 2-methylpropionic acid, avaleric acid, a 3-methylbutyric acid, a 2-methylbutyric acid, a2,2-dimethylpropionic acid (pivalic acid), a hexanoic acid, a2-methylvaleric acid, a 3-methylvaleric acid, a 4-methylvaleric acid, a2,2-dimethylbutyric acid, a 2,3-dimethylbutyric acid, a3,3-dimethylbutyric acid, a cyclopentanecarboxylic acid), and the like,and more preferably, the acetic acid, the propionic acid, the butyricacid, and the like. These solvents may be used in mixtures.

(Conditions for Acylation)

In carrying out the acylation, an acid anhydride, a catalyst, andoptionally a solvent may be mixed first, and then cellulose may be mixedwith these, or alternatively, the acid anhydride, catalyst and solventmay be separately and sequentially mixed with cellulose. However, it isusually preferable to prepare a mixture of an acid anhydride and acatalyst, or a mixture of an acid anhydride, a catalyst, and a solvent,as the acylating agent, and then to react the mixture with cellulose. Inorder to suppress temperature elevation in the reactor due to the heatof reaction upon acylation, the acylating agent is preferably cooled inadvance. The cooling temperature is preferably −50 to 20° C., morepreferably −35 to 10° C., and particularly preferably −25 to 5° C. Theacylating agent may be added in the liquid state, or in the solid stateby freezing the agent into a crystal, flake, or block form.

In addition, the acylating agent may be added all at once or may beadded in portions, to the cellulose. Alternatively, cellulose may beadded all at once or may be added in portions, to the acylating agent.In the case of when the acylating agent is added in portions, anacylating agent of identical composition may be used, or a plurality ofacylating agents of different compositions may be used. For preferredmethods, mention may be made of 1) a method of first adding a mixture ofan acid anhydride and a solvent and then adding a catalyst, 2) a methodof first adding a mixture of an acid anhydride, a solvent, and a portionof a catalyst, and then adding a mixture of the other potion of thecatalyst and a solvent, 3) a method of first adding a mixture of an acidanhydride and a solvent, and then a mixture of a catalyst and thesolvent, 4) a method of first adding a solvent, and then a mixture of anacid anhydride and a catalyst, or a mixture of an acid anhydride, acatalyst and a solvent, and the like.

The acylation of cellulose is an exothermic reaction, but for the methodfor producing cellulose acylate according to the aspect of theinvention, it is preferable if the maximum reached temperature duringacylation is 50° C. or lower. When the reaction temperature is 50° C. orlower, it is preferable because a situation where depolymerizationproceeds, making it difficult to obtain cellulose acylate having degreesof polymerization appropriate for the uses of the invention, or the likedoes not occur. The maximum reached temperature upon the acylation ispreferably 45° C. or lower, more preferably 40° C. or lower, even morepreferably 35° C. or lower, and particularly preferably 30° C. or lower.The reaction temperature may be controlled by using a temperatureadjusting device, or may be controlled by means of the initialtemperature of the acylating agent. The reaction temperature may be alsocontrolled by the heat of vaporization of liquid components in thereaction system, generated by pressure reduction in the reactor. Inaddition, since the exotherm of the acylation is significant at thebeginning of the reaction, the temperature may be controlled by coolingthe reaction system during the initiation of the reaction and thenheating the system, or the like. The termination point of the acylationmay be determined by such means as the light permeability, solutionviscosity, a change in temperature of the reaction system, solubility ofthe reactants to an organic solvent, observation with a polarizedmicroscope, and the like.

The minimum temperature of the reaction is preferably −50° C. or more,more preferably −30° C. or more, and particularly preferably −20° C. ormore. Time for acylation is preferably 0.5 to 24 hours, more preferably1 to 12 hours, and particularly preferably 1.5 to 6 hours. For 0.5hours, the reaction does not proceed sufficiently under normal reactionconditions, while the reaction time exceeding 24 hours is not preferablein the aspect of industrial production.

(Acyl Composition)

The degree of acylation preferably satisfies the following Formula B:0≦(MA/MB)≦2.0  Formula B

In Formula B, MA represents the total molar amount of the acetyl groupcontained in the reaction mixture for the acylation process.Specifically, MA is the summed molar amount of the acetyl groupcontained in the acylating agent, the acetyl group contained in thecarboxylic acid used for the pretreatment process, and the acetyl groupcontained in the produced cellulose acylate. MB represents the totalmolar amount of the acyl group having 3 to 7 carbon atoms contained inthe reaction mixture for the acylation process. Specifically, MB is thesummed molar amount of the acyl group having 3 to 7 carbon atomscontained in the acylating agent, the acyl group having 3 to 7 carbonatoms contained in the carboxylic acid used for the pretreatmentprocess, and the acyl group having 3 to 7 carbon atoms contained in theproduced cellulose acylate.

As such, the total molar amount of the acetyl group and the total molaramount of the acyl group having 3 to 7 carbon atoms are determined bythe compositions and amounts of the activating agent, acylating agent(acid anhydride and carboxylic acid) and solvent (carboxylic acid) usedin the pretreatment process. According to the aspect of the invention,the amount of the acyl group of acid anhydride is calculated in terms ofthe constituting carboxylic acid. That is, it is calculated such that 1mole of an acid anhydride is equivalent to 2 moles of an acyl group.Likewise, the number of moles of the acyl group in the producedcellulose acylate is calculated in terms of the carboxylic acidgenerated when all of the ester bonds are hydrolyzed. Although theamounts of the acid anhydride and carboxylic acid in the reactionmixture are sequentially changed as the acylation of cellulose proceeds,by performing the calculation, the total number of moles of all the acylgroups contained in the acid anhydride, carboxylic acid, and producedcellulose acylate in the reaction mixture is constant throughout theprocess of acylation, as long as no new acid anhydride or carboxylicacid is added to the reaction system.

The acylation process according to the aspect of the invention refers tothe period from the initiation of acylation of the hydroxyl groups ofcellulose to the point when substantially most of the hydroxyl groups ofthe cellulose are acylated (for example, the substitution degree for anacyl group is 2.0 or greater, preferably 2.5 or greater, more preferably2.8 or greater, and particularly preferably 2.9 or greater), and doesnot include the phase where the acylation is substantially almostcompleted, and further addition of acid anhydride or carboxylic acid tothe reaction system has virtually no effect on the acyl composition ofthe product cellulose acylate.

According to the aspect of the invention, MA/MB is preferably such that0<(MA/MB)≦2.0, more preferably 0.001≦(MA/MB)≦1.5, even more preferably0.01≦(MA/MB)≦1.0, and particularly preferably 0.05≦(MA/MB)≦0.7. WhenMA/MB exceeds 2, the substitution degree for an acetyl group of thecellulose acylate becomes excessively high, and there may be problemssuch as deterioration of stretchability, increase of the meltingtemperature for melt casting, resulting in difficult casting, and thelike.

(Reaction Terminating Agent)

According to the method for producing cellulose acylate used in theaspect of the invention, it is desirable to add a reaction terminatingagent after the acylation reaction.

For the reaction terminating agent, any substance capable of decomposingacid anhydrides may be used, and preferred examples thereof may includewater, alcohol (for example, ethanol, methanol, propanol, isopropylalcohol, etc.) or compositions containing these, and the like. Further,the reaction terminating agent may contain a neutralizing agent to bedescribed later. Upon addition of the reaction terminating agent, alarge exotherm surpassing the cooling capacity of the reactor apparatusis generated, possibly causing a decrease in the degree ofpolymerization of cellulose acylate, precipitation of cellulose acylateinto an undesired form, or the like. Thus, in order to avoid suchinconveniences, it is preferable to add a mixture of water and acarboxylic acid such as acetic acid, propionic acid, butyric acid, orthe like, rather than to directly add water or alcohol, and the aceticacid is particularly preferable as the carboxylic acid. The compositionratio of the carboxylic acid and water used may be at any arbitraryratio, but it is preferable to have the content of water in the range of5 to 80% by mass, more preferably 10 to 60% by mass, and particularlypreferably 15 to 50% by mass.

The reaction terminating agent may be added to the acylation reactor, orthe reactants may be added to the vessel of the reaction terminatingagent. The reaction terminating agent is preferably added over a timeperiod of 3 minutes to 3 hours. When the time for addition of thereaction terminating agent is 3 minutes or more, there does not occur asituation where the exotherm becomes excessively large, causing adecrease in the degree of polymerization, insufficient hydrolysis of theacid anhydride, reduced stability of the cellulose acylate, or the like,and thus it is desirable. When the time for addition of the reactionterminating agent is less than or equal to 3 hours, there does not occura problem such as deterioration of industrial productivity or the like,and it is desirable. The time for addition of the reaction terminatingagent is preferably 4 minutes to 2 hours, more preferably 5 minutes to 1hour, and particularly preferably 10 minutes to 45 minutes. Uponaddition of the reaction terminating agent, the reactor may be cooled ornot cooled, but for the purpose of inhibiting depolymerization, it isalso desirable to inhibit temperature increase by cooling the reactor.It is also preferable to have the reaction terminating agent cooled inadvance.

(Neutralizing Agent)

During the process of acylation reaction termination or after theprocess of acylation reaction termination, a neutralizing agent or itssolution may be added for the purpose of hydrolysis of the excessiveanhydrous carboxylic acid remaining in the system, neutralization ofpart or all of the carboxylic acid and esterification catalyst,adjustment of the amount of remaining sulfate radicals and the amount ofremaining metal, and the like.

Preferred examples of the neutralizing agent may include carbonates,hydrogen carbonates, organic acid salts (for example, acetates,propionates, butyrates, benzoates, phthalates, hydrogen phthalates,citrates, tartrates, etc.), phosphates, hydroxides, or oxides ofammonium, organic quaternary ammonium (for example, tetramethylammonium,tetraethylammonium, tetrabutylammonium, diisopropyldiethylammonium,etc.), alkali metals (preferably lithium, sodium, potassium, rubidium,and cesium, even more preferably lithium, sodium, and potassium, andparticularly preferably sodium and potassium), elements of Group 2(preferably beryllium, calcium, magnesium, strontium, barium, beryllium,calcium, and magnesium, and particularly preferably calcium andmagnesium), metals of Groups 3 to 12 (for example, iron, chromium,nickel, copper, lead, zinc, molybdenum, niobium, titanium, etc.), orelements of Groups 13 to 15 (for example, aluminum, tin, antimony,etc.), and the like. These neutralizing agents may be used in mixtures,or may form mixed salts (for example, magnesium acetate propionate orpotassium sodium tartrate). In the case of when the anion of suchneutralizing agent is divalent or higher, the agent may form hydrogensalts (for example, sodium hydrogen carbonate, potassium hydrogencarbonate, sodium dihydrogen phosphate, magnesium hydrogen phosphate,etc.).

More preferred examples of the neutralizing agent include carbonates,hydrogen carbonates, organic acid salts, hydroxides, or oxides ofammonium, alkali metals, elements of Group 2, or elements of Group 13,or the like, and particularly preferred examples include carbonate,hydrogen carbonate, acetate, or hydroxide of sodium, potassium,magnesium, or calcium.

Preferred examples of the solvent for the neutralizing agent may includewater, alcohols (for example, ethanol, methanol, propanol, isopropylalcohol, etc.), organic acids (for example, acetic acid, propionic acid,butyric acid, etc.), ketones (for example, acetone, ethyl methyl ketone,etc.), polar solvents such as dimethylsulfoxide, and solvent mixturesthereof.

(Partial Hydrolysis)

The cellulose acylate thusly purchased has a substitution degree for anacyl group of nearly 3, but for the purpose of obtaining celluloseacylate of desired substitution degree, a process of partiallyhydrolyzing the ester bonds by maintaining the cellulose acylate at 20to 90° C. for a few minutes to a few days in the presence of a smallamount of catalyst (generally an acylation catalyst such as remainingsulfate) and water, in order to reduce the substitution degree for anacyl group of the cellulose acylate to a desired degree (so-calledaging) is usually carried out. The amount of the sulfuric acid esterbound to the cellulose can be reduced in the process of partialhydrolysis by also allowing hydrolysis of the sulfuric acid ester ofcellulose, and by adjusting the conditions for hydrolysis.

(Termination of Partial Hydrolysis)

It is preferable to terminate the partial hydrolysis at the time pointof obtaining the desired cellulose acylate by completely neutralizingthe catalyst remaining in the system using a neutralizing agent or itssolution as described above.

In the case of when a sulfuric acid is used as the catalyst, the amountof the neutralizing agent added to the reaction mixture is preferably anexcessive equivalent amount with respect to the sulfate radicals (freesulfuric acid or cellulose-bound sulfuric acid). According to the aspectof the invention, the neutralizing agent may be added in portions, butit is desirable to add the neutralizing agent after completion of thepartial hydrolysis (aging) so that the amount of the neutralizing agentis an excessive equivalent amount with respect to the sulfate radicals.The sulfuric acid bound to the cellulose (cellulose sulfate) is amonovalent acid, but the equivalent of the neutralizing agent iscalculated in terms of free sulfuric acid. Thereby, the equivalent ofthe neutralizing agent may be determined from the amount of the sulfuricacid added. A preferred amount of the neutralizing agent to be added ispreferably 1.2 to 50 equivalents, more preferably 1.3 to 20 equivalents,and particularly preferably 1.5 to 10 equivalents, with respect tosulfate radicals.

It is also desirable to effectively remove the catalyst (for example,sulfuric acid ester) in the solution or bound to the cellulose by addinga neutralizing agent which produces a salt of low solubility to thereaction solution (for example, magnesium carbonate, magnesium acetate,etc.).

(Post-Heating Process)

The reaction mixture after the termination of the partial hydrolysis ispreferably further maintained at 30 to 100° C. for at least one hour(post-heating process). By carrying out this process, a celluloseacylate having good thermal stability may be purchased by reducing theamount of the sulfuric acid bound to cellulose acylate. As to the reasonfor the reduction of the amount of the sulfuric acid bound to celluloseacylate in this process, although details have not been clarified, it isbelieved that heating a cellulose acylate solution in the presence ofbase in excess leads to gradual de-esterification of the sulfuric acidester which is more likely to undergo hydrolysis than acyl ester, andfree sulfuric acid that is neutralized by the base drives theequilibrium to be lopsided to the production system and thus promotesthe reaction.

For the post-heating process, the maintenance temperature is preferably30 to 100° C., more preferably 40 to 100° C., even more preferably 50 to90° C., and particularly preferably 60 to 80° C. When the temperature isset to 30° C. or more, the effect of reducing the amount of boundsulfuric acid is easily purchased, while when the temperature is set to100° C. or less, the process is improved in the aspect of operability orsafety. Additionally, for the post-heating process, the time formaintenance is preferably 1 to 100 hours, more preferably 2 to 100hours, and particularly preferably 2 to 50 hours. When the time is setto 1 hour or more, the amount of bound sulfuric acid is efficientlyreduced, while when the time is set to 100 hours or less, industrialproductivity is improved. For the post-heating process, the reactionmixture is preferably stirred. Furthermore, the neutralizing agent maybe further added during the post-heating process.

(Re-Precipitation)

The Desired Cellulose Acylate May be Purchased by mixing the celluloseacylate solution thusly purchased into a poor solvent such as waterand/or an aqueous carboxylic acid solution (for example, acetic acid,propionic acid, butyric acid, etc.), or by mixing a poor solvent intothe cellulose acylate solution to re-precipitate the cellulose acylate,and washing and stabilizing the purchased cellulose acylate. There-precipitation may be carried out continuously or in a batch mode withdefinite amounts. It is also preferable to control the form or molecularweight distribution of the re-precipitated cellulose acylate byadjusting the concentration of the cellulose acylate solution and thecomposition of the poor solvent by means of the mode of substitution ordegree of polymerization of the cellulose acylate.

Furthermore, for the purpose of purifying cellulose acylate by using aproduction method other than the method according to the aspect of theinvention, improving the purification effect of cellulose acylate byusing the production method according to the aspect of the invention,adjusting the molecular weight distribution or apparent density, or thelike, the operation of conducting re-precipitation may be carried outonce or several times, as needed, by re-dissolving the oncere-precipitated cellulose acylate in a good solvent (for example, aceticacid, acetone, etc.), performing the filtration, and subjecting thesolution to a poor solvent (for example, water, carboxylic acid (forexample, acetic acid, propionic acid, butyric acid), etc.). Inconnection with this, it is preferable that the solvent and the poorsolvent be filtered in advance to remove fine impurities therefrom.

(Washing)

The produced cellulose acylate is preferably subjected to washing. Thewashing solvent may be any one that has low dissolvability for celluloseacylate and is capable of removing impurities, but usually washing watersuch as water or warm water is used. The temperature of the washingwater is preferably 20 to 100° C., more preferably 30 to 95° C., andparticularly preferably 40 to 95° C. The temperature during the washingprocess may be constant or may vary within an arbitrary temperaturerange; however, the invention preferably comprises a step of washing thecellulose acylate at preferably 40 to 95° C., more preferably 50 to 95°C., and particularly preferably 60 to 90° C., for preferably 1 to 100hours, more preferably 2 to 50 hours, and particularly preferably 3 to10 hours. The above-described washing process at 40 to 95° C. andanother washing process in another temperature range may be combined.

The washing treatment may be carried out in a so-called batch mode wherealternation of filtration and washing liquid is repeated, or may becarried out using a continuous washing apparatus. It is preferable toreuse the waste water generated in the re-precipitation and washingprocesses as the poor solvent for the re-precipitation process, or torecover the solvent such as carboxylic acid by means of distillation orthe like and reuse the solvent.

The course of washing may be traced by any means, but preferred examplesmay include methods involving hydrogen ion concentration, ionchromatography, electric conductivity, ICP, elemental analysis, atomicabsorption spectrum, and the like.

Such treatment allows removal of the catalyst (a sulfuric acid, aperchloric acid, a trifluoroacetic acid, a p-toluenesulfonic acid, amethanesulfonic acid, zinc chloride, etc.) of cellulose acylate, theneutralizing agent (for example, carbonate, acetate, hydroxide, or oxideof calcium, magnesium, iron, aluminum, or zinc, etc.), the reactionproduct between the neutralizing agent and the catalyst, the carboxylicacid (acetic acid, propionic acid, butyric acid, etc.), the reactionproduct between the neutralizing agent and carboxylic acid, and thelike, and thus is effective in enhancing the stability of the celluloseacylate.

(Stabilization)

It is also preferable to treat the cellulose acylate, after the washingby warm water treatment, with an aqueous solution of weak alkali (forexample, carbonate, hydrogen carbonate, hydroxide, oxide, or the like ofsodium, potassium, calcium, magnesium, aluminum, or the like), in orderto further enhance the stability or to reduce the odor of the carboxylicacid. In this connection, it is preferable that the solution of the usedstabilizer be filtered to remove contained fine impurities therefrom.

The amount of remaining impurities may be controlled by the metalcontent in the water used (the amount of metal ions contained in thewater used as washing water or the like as trace components), the amountof the washing liquid, the washing temperature, time, agitation method,the form of the washing vessel, or the composition or concentration ofthe stabilizer. According to the aspect of the invention, the conditionsfor the acylation, partial hydrolysis, neutralization, and washing arepreferably set such that the amount of remaining sulfate radicals (interms of the content of sulfur atoms) is 50 to 500 ppm. The amount ofremaining alkali metal and the amount of Group 2 element also may beadjusted by the conditions of partial hydrolysis, neutralization, andwashing.

According to the aspect of the invention, preferably, a ratio (M/S) of amolar content (M) of alkali metals (potassium, sodium, etc.) andelements of Group 2 (magnesium, calcium, etc.) to a molar content (S) ofremaining sulfate radicals that are contained in cellulose acylate is0.5 to 3. Furthermore, it is preferable that a potassium content be 25ppm or less and a sodium content be 25 ppm or less.

In the case of when the cellulose acylate satisfies the above-mentionedrelation, thermal stability may be made good. The lower limits ofcontents of potassium and sodium are not limited.

(Drying)

In order to adjust the water content in the cellulose acylate to apreferred amount in the aspect of the invention, it is desirable to drythe cellulose acylate. The method of drying is not particularly limitedas long as the desired water content can be purchased, but it ispreferable to carry out the drying efficiently by using the means suchas heating, blow drying, pressure reduction, and agitation individuallyor in combination. The drying temperature is preferably 0 to 200° C.,more preferably 40 to 180° C., and particularly preferably 50 to 160° C.The cellulose acylate according to the aspect of the invention has awater content of preferably 2 wt % or less, more preferably 1 wt % orless, and particularly preferably 0.7 wt % or less.

(Filtration)

According to the aspect of the invention, the solution in whichcellulose acylate that satisfies at least formulae 1 to 3 and has a meltviscosity of 150 to 1000 Pa·s at 230° C. is dissolved in the solvent isfiltered by using a filter having a retention particle size of 0.1 to 40μm. In addition to the filtration according to the aspect of theinvention, the cellulose acylate may be filtered by using a reactionmixture (dope) in order to remove or reduce unreacted substances,insoluble salts, and other impurities from the cellulose acylate incellulose during the production of the cellulose acylate. The filtrationmay be performed at any step between the acylation and there-precipitation. Preferably, the filtration is performed immediatelybefore the re-precipitation.

The retention particle diameter of the filter that is used to performthe filtration is preferably 0.1 to 50 μm, more preferably 0.5 to 40 μm,and particularly preferably 1 to 30 μm. If the retention particlediameter of the filter is set to 0.1 μm or more, since an increase infiltration pressure is not significant, industrial production thereof isapt to be easily achieved. Furthermore, the retention particle diameterof the filter may be set to 40 μm or less to easily remove theimpurities. In addition, the filtration may be repeated twice or more.

The material of the filter is not limited as long as the material is notnegatively affected by the solvent. Preferable examples of the materialof the filter may include a cellulose-based filter, a metal filter, asintered metal filter, a sintered ceramic filter, a Teflon filter (PTFEfilter) (Teflon®), a polyethersulfone filter, a polypropylene filter, apolyethylene filter, a glass fiber filter, or a mixture thereof. Amongthem, the metal filter that is made of stainless steel and the sinteredmetal filter are preferable.

As to the type of the material of the filter, the filter having anelectric charge capture ability may be preferably used. The filterhaving the electric charge capture ability means the filter that has anability capable of capturing and removing the electrically chargedimpurities. Generally, in the filter, electric charges are provided to afiltration material. Examples of the filter may include filters that aredisclosed in JP-T-1992-504379 and JP-A-2000-212226.

Preferably, a dead-end filtration process in which sellite, layered clayminerals (preferably, talc, mica, kaolinite, and the like), and the likeare mixed with the cellulose acylate solution and the resulting mixtureis filtered is used.

In order to control the filtration pressure or handlability, it ispreferable to perform dilution using a suitable solvent before thefiltration.

(Solvent)

According to the aspect of the invention, the solution in whichcellulose acylate that satisfies at least formulae 1 to 3 and has a meltviscosity of 150 to 1000 Pa·s at 230° C. is dissolved in the solvent isfiltered by using a filter having a retention particle size of 0.1 to 40μm. Any solvent may be used in respect to the cellulose acylate as longas solubility of the cellulose acylate is high. Preferable examples ofthe solvent may include a carboxylic acid (formic acid, an acetic acid,a propionic acid, a butyric acid, and the like), ketone (aceton, ethylmethyl ketone, ethyl isobutyl ketone, and the like), ester (methylacetate, ethyl acetate, acetic acid butyl, acetic acid isopropyl, andthe like), a halogen-based solvent (dichloromethane, chloroform,dichloroethane, and the like), and the like. The above-mentionedsolvents may be used singly or in a mixture form containing two or moresolvents.

More preferable examples of the solvent include a carboxylic acid (anacetic acid, a propionic acid, a butyric acid, and the like), ketone(aceton, ethyl methyl ketone, ethyl isobutyl ketone, and the like), andthe like. Particular preferable examples of the solvent include acarboxylic acid (an acetic acid, a propionic acid, and the like) andketone (acetone and the like).

Preferable examples of the poor solvent that is used during there-precipitation may include water, alcohols (methanol, ethanol,isopropyl alcohol, butanol, and the like), hydrocarbon-based solvents(pentane, hexane, heptane, toluene, and the like). The above-mentionedpoor solvents may be used singly or in a mixture form containing two ormore solvents. A mixture of the poor solvent and another solvent may beused without deviation from the scope of the invention.

More preferable examples of the poor solvent include water and alcohols(methanol, ethanol, isopropyl alcohol, and the like), and particularpreferable examples of the poor solvent include water and alcohols(methanol and the like).

(Specific Procedure of the Filtration Process)

The retention particle diameter of the filter that is used to performthe filtration is preferably 1 to 30 μm, more preferably 1 to 20 μm, andparticularly preferably 2 to 20 μm. The retention particle diameter ofthe filter is set to 0.1 μm or more to prevent filtration pressure frombeing significantly increased and to easily perform industrialproduction thereof. Furthermore, the retention particle diameter of thefilter may be set to 40 μm or less to easily remove the impurities andto improve optical performance of the purchased film. In addition, thefiltration may be repeated twice or more, and the filters havingdifferent retention particle sizes may be used in combination.

The filtration may be performed at any temperature as long as thefiltration is capable of being performed. However, it is possible toreduce the viscosity of the solution when the filtration temperature ispreferably 30 to 100° C., more preferably 35 to 80° C., and particularlypreferably 40 to 70° C.

Furthermore, in respect to the filtration pressure, the filtration isperformed at preferably 0.001 to 10 MPa, more preferably 0.001 to 5 MPa,and particularly preferably 0.01 to 1 MPa.

According the aspect of the invention, a solution where the carboxylicacid is added to the cellulose acylate may be filtered by using a filterhaving a retention particle size of 0.1 to 40 μm at any step between anearly step of the acylation process and the re-precipitation process inorder to efficiently remove or reduce unreacted substances, insolublesalts, and other impurities from the cellulose acylate in celluloseduring the production of the cellulose acylate. The retention particlesize may be purchased according to the method that is disclosed in JIS P3801.

Particularly, according to the aspect of the invention, if thefiltration is performed immediately before the reprecipitation process,this is preferable in views of stability of quality of products and areduction in filtration viscosity. In the case of when the filtration isperformed through two stages, it is preferable that rough filtration beperformed by using a filter having a retention particle size of 20 to 40μm and additional filtration be performed by using a filter having aretention particle size of 0.1 to 20 μm. Preliminary filtration may beperformed by using a filter having a retention particle size of 40 to100 μm before the filtration according to the aspect of the invention.

In the production method according to the aspect of the invention, thematerial of the filter is not limited as long as the material is notnegatively affected by the solvent. Preferable examples of the materialof the filter may include a cellulose-based filter, a metal filter, asintered ceramic filter, a Teflon filter (PTFE filter), apolyethersulfone filter, a polypropylene filter, a polyethylene filter,a glass fiber filter, or a mixture thereof.

As to the type of the material of the filter, the filter having anelectric charge capture ability may be preferably used. The filterhaving the electric charge capture ability means the filter that has anability capable of capturing and removing the electrically chargedimpurities. Generally, in the filter, electric charges are provided to afiltration material. Examples of the filter may include filters that aredisclosed in JP-T-1992-504379 and JP-A-2000-212226.

Preferably, a dead-end filtration process in which sellite, layered clayminerals (preferably, talc, mica, kaolinite, and the like, and morepreferably talc), and the like are mixed with the cellulose acylatesolution and the resulting mixture is filtered is used.

In order to control the filtration pressure or handlability, it ispreferable to perform dilution using a suitable solvent before thefiltration.

The filtration may be selected from pressure filtration, vacuumfiltration, or normal pressure filtration, but it is preferable toperform the pressure filtration.

(Amount of Impurity)

The amount of impurity that is contained in a cellulose acylatecomposition according to the aspect of the invention and has a particlesize of 40 μm or more is preferably 0.1 particles/g or less, morepreferably 0.05 particles/g or less, and particularly preferably 0.01particles/g or less.

The amount of the impurity may be measured by using a microscope and alight scattering type of particle detector. The shape of impurity isgenerally a needle or a particle, but is not limited thereto. In theaspect of the invention, in respect to the amount of impurity, theimpurity contains unreacted cellulose, impurity added from the outside,gellated substances, and side products which are not compatible with thecellulose acylate.

(Degree of Polymerization)

The molecular weight of the cellulose acylate that is used in the aspectof the invention is a weight average molecular weight which is purchasedby using a gel permeation chromatography method (GPC method) and 80,000to 180,000. The weight average molecular weight is preferably 90,000 to190,000, and more preferably 100,000 to 180,000.

If the weight average molecular weight is set to 180,000 or less, sincethe melt viscosity is not significantly high, the casting is apt to beeasily performed. Meanwhile, if the weight average molecular weight isset to 80,000 or more, since the melt viscosity is not significantlyreduced while the required strength of the film is maintained, thecutting may be desirably performed during the kneading. Accordingly,this is preferable because the kneading is desirably performed.

The average molecular weight may be measured by the intrinsic viscositymethod of Uda et al. (Kazuo Uda and Hideo Saito: Journal of the Societyof Fiber Science and Technology, Japan, Vol. 18, No. 1, pp. 105-120,1962), in addition to the molecular weight distribution measurement byGPC, or the like. These are described in detail in JP-A-1997-95538.

According to the aspect of the invention, the weight average molecularweight/number average molecular weight of the cellulose acylate ispreferably 1.0 to 5, more preferably 1.3 to 4, and particularlypreferably 1.5 to 3.5.

The average substitution degree for the substituent according to theaspect of the invention may be determined by ¹H-NMR or ¹³C-NMR.

According to the aspect of the invention, two or more different types ofcellulose acylates may be used in a mixture or separately.

(Form)

In the production method according to the aspect of the invention, thesolution, the melt, the gel, the pellet, or the film is preferable, andthe pellet or the film is more preferable.

The pellet can be in various forms such as particulate form, powderedform, fiber form, lump form, or the like.

However, since the particulate form or powdered form is preferable forthe raw material for cellulose acylate film production, the driedcellulose acylate composition may be pulverized or sieved for thepurpose of uniformizing the particle size or improving the handlability.When the cellulose acylate composition is in the particulate form, 90 wt% or greater of the particles used preferably have a particle size of0.5 to 5 mm. Also, 50 wt % or greater of the particles used preferablyhave a particle size of 1 to 4 mm. The cellulose acylate compositionparticles preferably have a shape proximate to the spherical shape asmuch as possible. Furthermore, the cellulose acylate composition that isproduced by using the production method according to the aspect of theinvention preferably has an apparent density of 0.5 to 1.3 g/cm³, morepreferably 0.7 to 1.2 g/cm³, and particularly preferably 0.8 to 1.15g/cm³. The method for measuring the apparent density is provided in JISK-7365.

The cellulose acylate composition that is purchased by the productionmethod according to the aspect of the invention has an angle of reposeof preferably 10 to 70°, more preferably 15 to 60°, and particularlypreferably 20 to 50°.

<Optical Properties of the Cellulose Acylate Film>

Next, the cellulose acylate film that is produced by the productionmethod according to the aspect of the invention will be described.Preferably, the cellulose acylate film that is produced by theproduction method according to the aspect of the invention satisfies thefollowing formulae i and ii.−500 nm≦Re≦500 nm  Formula i−500 nm≦Rth≦500 nm  Formula ii

Re is more preferably −100 to 250 nm and particularly preferably 0 to150 nm. Rth is more preferably −200 to 400 nm and particularlypreferably −100 to 300 nm.

[Retardation]

First, in the aspect of the invention, the retardation will bedescribed. In this specification, Re and Rth (unit; nm) are measured byusing the following method. After the film is subjected to humidityconditioning at 25° C. and a relative humidity of 60% for 24 hours, anaverage refractive index (n) that is represented by the followingFormula a is purchased by means of a prism coupler (MODEL 2010 PrismCoupler: manufactured by Metricon, Co.) using a solid laser of 532 nm at25° C. and a relative humidity of 60%.n=(nTE×2+nTM)/3  Formula awherein, nTE is a refractive index measured by in-plane polarized lightof the film and nTM is a refractive index measured by polarized light ina direction perpendicular to the film surface.

According to this specification, Re (λ) and Rth (λ) represent thein-plane retardation and the retardation in the thickness direction,respectively, at a wavelength of λ. Re (λ) is measured using KOBRA 21ADHor WR (manufactured by Oji Scientific Instruments, Ltd.), by radiatinglight at a wavelength of λ nm incidentally to the direction normal tothe film.

In the case of when the film to be measured is represented as a uniaxialor biaxial optical indicatrix, Rth (λ) is calculated by the followingmethod.

For Rth (λ), the above-described Re (λ) is measured at eleven points bytaking the in-plane retardation axis (determined by KOBRA 21ADH or WR)as the tilting axis (rotating axis) (when there is no retardation axis,an arbitrary direction in the film plane is taken as the rotating axis),and radiating light at a wavelength of λ nm incidentally to the filmnormal direction, from the respective tilting directions selected in aninterval of 10° in the range from the normal direction to +50° on eitherside, and Rth (λ) is calculated based on the measured retardationvalues, assumed values for the average refractive indices, and the inputfilm thickness, by using KOBRA 21ADH or WR.

In this connection, in the case of when a description is not given of λbut only “Re” and “Rth” are described, the value that is measured byusing light at a wavelength of 590 nm is given. In this regard, in thecase of a film having a direction in which the retardation value wouldbe zero at a certain tilting angle in the range of from the normaldirection to the in-plane retardation axis as the rotating axis, it iscalculated by KOBRA 21ADH or WR, after changing the symbol of theretardation value at a tilting angle larger than the above-mentionedtilting angle, to negative.

Furthermore, Rth may be measured from any two tilting directions, whiletaking the retardation axis as the tilting axis (rotating axis) (whenthere is no retardation axis, any direction in the film plane is takenas the rotating axis), based on the values, an assumed value for theaverage refractive index, and the input film thickness, according to thefollowing Formula b and Formula c.

$\begin{matrix}{\mspace{20mu}{{{Re}(\theta)} = {\quad{\left\lbrack {{nx} - \frac{{ny} \times {nz}}{\sqrt{\begin{matrix}{\left( {{ny}\mspace{11mu}{\sin\left( {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2} +} \\\left( {{nz}\mspace{11mu}{\cos\left( {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2}\end{matrix}}}} \right\rbrack \times \frac{d}{\cos\left( {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right)}}}}} & {{Formula}\mspace{14mu} b}\end{matrix}$wherein, Re(θ) represents the retardation value in a direction tiltingfrom the normal direction at an angle of θ. nx represents the refractiveindex in the in-plane retardation axis, ny represents the refractiveindex in a direction perpendicular to the in-plane nx, and nz representsthe refractive index in a direction perpendicular to nx and ny.Rth=((nx+ny)/2−nz)×d  Formula c

In the case of when a film to be measured cannot be represented as auniaxial or biaxial optical indicatrix, that is, in the case of when thefilm does not have so-called an optic axis, Rth (λ) is calculated by thefollowing method.

For Rth (λ), the above-mentioned Re (λ) is measured at 11 points bytaking the in-plane retardation axis (determined by KOBRA 21ADH or WR)as the tilting axis (rotating axis) (when there is no retardation axis,an arbitrary direction in the film plane is taken as the rotating axis),and radiating a light at a wavelength of λ nm incidentally to the filmnormal direction, from the respective tilting directions selected in aninterval of 10° in the range from −50° to +50° with respective to thefilm normal direction, and Rth (λ) is calculated based on the measuredretardation values, assumed values for the average refractive indices,and the input film thickness, by using KOBRA 21ADH or WR.

When these assumed values of average refractive indices and filmthicknesses are input, nx, ny, and nz are calculated by using the KOBRA21ADH or WR. Nz=(nx−nz)/(nx−ny) is calculated by using these calculatednx, ny, and nz.

The method for producing the cellulose acylate film according to theaspect of the invention is not limited, but it is preferable that theproduction be performed by using the following melt casting method orsolution casting method. Since a load to filtration that is performedduring the casting process is significantly reduced, it is morepreferable to perform the casting by using the melt casting.

<Melt Casting>

In the aspect of the invention, the cellulose acylate film can beproduced by using the melt casting method.

In the aspect of the invention, the cellulose acylate may be used singlyor as a mixture containing two or more thereof. Furthermore, polymercomponents other than the cellulose acylate used in the aspect of theinvention, or various types of additives may be appropriately added. Itis preferable to add the components that have excellent compatibility tothe cellulose acylate. Permeability of the resulting film is preferably80% or more, more preferably 90% or more, and particularly preferably92% or more.

The melt viscosity of the cellulose acylate composition that is appliedto the melt casting at 230° C. (the melt viscosity of the producedcellulose acylate film at 220° C.) is 150 to 1000 Pa·s. Theabove-mentioned melt viscosity can be purchased when the compositions ofthe substituents satisfy formulae 1 to 3 and their molecular weights arecontrolled.

(Stabilizer)

In the aspect of the invention, it is desirable to add a stabilizer inorder to maintain stability of the cellulose acylate during the hightemperature melt casting. Particularly, it is preferable to add at leastone phenol-based stabilizer having a molecular weight of 500 or more andat least one of a phosphorous acid ester-based stabilizer and athioether-based stabilizer having a molecular weight of 500 or more. Aknown phenol-based stabilizer may be used as a preferable phenol-basedstabilizer. Preferable examples of the phenol-based stabilizer mayinclude a hindered phenol-based stabilizer. Particularly, it ispreferable that the phenol-based stabilizer have a substituent adjacentto a phenol-based hydroxyl group. In this case, a substituted orunsubstituted alkyl group having 1 to 22 carbon atoms is preferable asthe substituent, and a methyl group, an ethyl group, a propionyl group,an isopropionyl group, a butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a tert-pentyl group, a hexylgroup, an octyl group, an isooctyl group, and a 2-ethylhexyl group aremore preferable. In addition, preferable examples of material mayinclude a stabilizer that has a phenol group and a phosphorous acidester group in the same molecule.

The stabilizer can be commercially purchased and is sold by thefollowing makers. Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245,Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganox 1035,Irganox 1098, and Irganox 1425WL can be purchased from Ciba SpecialtyChemicals, Inc. Furthermore, ADK STAB AO-50, ADK STAB AO-60, ADK STABAO-20, ADK STAB AO-70, and ADK STAB AO-80 can be purchased from ADEKACORPORATION. Furthermore, sumilizer BP-76, sumilizer BP-101, andsumilizer GA-80 can be purchased from Sumitomo Chemical Co., Ltd.Furthermore, SEENOX 326M and SEENOX 336B can be purchased fromSHIPROKASEI KAISYA, Ltd.

Furthermore, it is preferable to contain a phosphorous acid ester-basedstabilizer that has a molecular weight of 500 or more and an oxidationprevent effect. Examples of these compounds may include compoundsdisclosed in paragraph Nos. [0023] to [0039] of JP-A-2004-182979 andmixtures disclosed in JP-A-1976-70316, JP-A-1998-306175,JP-A-1982-78431, JP-A-1979-157159, and JP-A-1980-13765. Otherstabilizers may be selected from materials disclosed in detail in pages17 to 22 of the Journal of Technical Disclosure of Japan Institute ofInvention and Innovation (Article No. 2001-1745, published on Mar. 15,2001, Japan Institute of Invention and Innovation). As to examplesthereof, ADK STAB 1178, ADK STAB 2112, ADK STAB PEP-8, ADK STAB PEP-24G,PEP-36G, and ADK STAB HP-10 of ADEKA CORPORATION, and Sandostab P-EPQ ofClariant, Co. are placed on the market and can be purchased. As to athioether stabilizer, a known thioether-based stabilizer may be used.Sumilizer TPL, sumilizer TPM, sumilizer TPS, and sumilizer TDP ofSumitomo Chemical Co., Ltd are placed on the market as the thioetherstabilizer. ADK STAB AO-412S of ADEKA CORPORATION is capable of beingpurchased. In the case of when these stabilizers are used, it ispreferable that at least one of phenol-based stabilizers and at leastone of a phosphorous acid ester-based stabilizer and a thioether-basedstabilizer be each contained in an amount of 0.02 to 3% by mass inrespect to cellulose acylate. Particularly, it is preferable that theamount be 0.05 to 1% by mass. The ratio of amounts of the phenol-basedstabilizer and the phosphorous acid ester-based stabilizer or thethioether-based stabilizer is not limited, but preferably 1/10 to 10/1(parts by mass), more preferably 1/5 to 5/1 (parts by mass), even morepreferably 1/3 to 3/1 (parts by mass), and particularly preferably 1/3to 2/1 (parts by mass).

According to the aspect of the invention, the stabilizer that has aphenol group and a phosphorous acid ester group in the same molecule isused. These materials are disclosed in JP-A-1998-273494. Sumilizer GP(Sumitomo Chemical Co., Ltd) may be used as commercial products.Furthermore, long-chain aliphatic amine that is disclosed inJP-A-1986-63686, a compound containing a steric barrier amine group thatis disclosed in JP-A-1994-329830, a hindered piperidinyl-based lightstabilizer that is disclosed in JP-A-1995-90270, and an organic aminethat is disclosed in JP-A-1995-278164 may be used. ADK STAB LA-57, ADKSTAB LA-52, ADK STAB LA-67, ADK STAB LA-62, and ADK STAB LA-77 of ADEKACORPORATION and TINUVIN 765 and TINUVIN 144 of Ciba Specialty ChemicalsInc. are placed on the market as the preferable amine-based stabilizer.The ratio of amines to phosphorous acid esters is generally 0.01 to 25%by mass.

(Plasticizer)

If a plasticizer is added to cellulose acylate during the casting, thecrystal melt temperature (Tm) of the cellulose acylate may be reduced.The molecular weight of the plasticizer that is used in the aspect ofthe invention is not limited, but preferably 500 or more, morepreferably 550 or more, and particularly preferably 600 or more which ishigh.

Examples of the plasticizer may include phosphoric acid esters,alkylphthalylalkyl glycolates, carboxylic acid esters, fatty acid estersof polyhydric alcohol, and the like. The plasticizer may be in a solidform or oily form. That is, the melting point or boiling point thereofis not limited. In the case of when the melt casting is performed, it isparticularly preferable to use the matter having nonvolatility.

Examples of the phosphoric acid ester may include triphenyl phosphate,tricresyl phosphate, phenyl diphenyl phosphate, and the like.

Examples of the alkylphthalylalkyl glycolates may includemethylphthalylmethyl glycolate, ethylphthalylethyl glycolate,propylphthalylpropyl glycolate, butylphthalylbutyl glycolate,octylphthalyloctyl glycolate, methylphthalylethyl glycolate,ethylphthalylmethyl glycolate, ethylphthalylpropyl glycolate,methylphthalylbutyl glycolate, ethylphthalylbutyl glycolate,butylphthalylmethyl glycolate, butylphthalylethyl glycolate,propylphthalylbutyl glycolate, butylphthalylpropyl glycolate,methylphthalyloctyl glycolate, ethylphthalyloctyl glycolate,octylphthalylmethyl glycolate, octylphthalylethyl glycolate, and thelike.

Examples of the carboxylic acid esters may include phthalic acid esterssuch as dimethyl phthalate, diethyl phthalate, dibutyl phthalate,dioctyl phthalate, and diethylhexyl phthalate, and citric acid esterssuch as acetyltrimethyl citrate, acetyltriethyl citrate, andacetyltributyl citrate. In addition to these, it is favorable to usebutyl oleate, methylacetyl linolate, dibutyl sebacate, triacetin and thelike individually or in combination.

The amount of these plasticizers is preferably 0 to 15% by mass, morepreferably 0 to 10% by mass, and particularly preferably 0 to 8% bymass, with respect to the cellulose acylate composition. Theseplasticizers may be used in combination of two or more species, ifnecessary.

(Stabilizer)

According to the aspect of the invention, it is preferable to add atleast one of stabilizers to the material constituting the film before orduring the melting of the cellulose acylate by heating. These are usefulto prevent oxidation of the material constituting the film, capture ofacids generated due to the decomposition, suppress or prevent thedecomposition reaction due to radical species by light or heat, andsuppress the decomposition reaction that is not explained and thegeneration of volatile components due to deterioration such as coloringor a reduction in molecular weight or decomposition of the material. Inrespect to the melt temperature for casting, it is required that thestabilizer is not decomposed. The stabilizer may be appropriatelyselected according to the purpose.

Examples of the material of the stabilizer may include a phenol-basedstabilizer, a phosphorous acid-based stabilizer (phosphates), athioether-based stabilizer, an amine-based stabilizer, an epoxy-basedstabilizer, a lactone-based stabilizer, an amine-based stabilizer, ametal deactivating agent (tin-based stabilizer), and the like. These aredisclosed in JP-A-1991-199201, JP-A-1993-1907073, JP-A-1993-194789,JP-A-1993-271471, JP-A-1994-107854, and the like.

According to the aspect of the invention, the stabilizer may be usedsingly or in combination of two or more species, and the mixing amountis appropriately selected within the range where an advantage of theinvention is not obstructed. The amount of stabilizer added ispreferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, andparticularly preferably 0.01 to 0.8% by mass based on the mass of thecellulose resin.

(Phenol-Based Stabilizer)

According to the aspect of the invention, the hindered phenol-basedstabilizer that is useful as the compound used to perform stabilizationin the course of melting the material constituting the film by heatingis a known compound, for example, a 2,6-dialkylphenol derivativecompound that is disclosed in paragraphs 12 to 14 of U.S. Pat. No.4,839,405.

Among them, it is particularly preferable to add the phenol-basedstabilizer having the molecular weight of 500 or more. Preferableexamples of the phenol-based stabilizer may include a hinderedphenol-based stabilizer.

These materials are commercial products, capable of being easilypurchased, and sold by the following makers. Irganox 1076, Irganox 1010,Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259,Irganox 565, Irganox 1035, Irganox 1098, and Irganox 1425WL of CibaSpecialty Chemicals, Inc. are capable of being purchased. Furthermore,ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADKSTAB AO-80 of ADEKA CORPORATION are capable of being purchased.Furthermore, sumilizer BP-76, sumilizer BP-101, and sumilizer GA-80 ofSumitomo Chemical Co., Ltd are capable of being purchased. Furthermore,SEENOX326M and SEENOX336B of SHIPROKASEI KAISYA, Ltd. are capable ofbeing purchased.

(Phosphorous Acid-Based Stabilizer)

The phosphorous acid ester-based stabilizer according to the aspect ofthe invention has a high molecular weight in order to maintain stabilityat high temperatures, and the molecular weight thereof is preferably 500or more, more preferably 550 or more, and particularly preferably 600 ormore. In addition, it is preferable that at least one substituent be anaromatic ester group. Furthermore, the phosphorous acid ester-basedstabilizer is preferably trimester, and it is preferable that impuritiessuch as a phosphoric acid, monoester, or diester are not mixedtherewith. In the case of when the impurity is present, the amount ispreferably 5% by mass or less, more preferably 3% by mass or less, andparticularly preferably 2% by mass or less. Examples of them may includecompounds that are disclosed in paragraphs [0023] to [0039] ofJP-A-2004-182979, and compounds that are disclosed in JP-A-1976-70316,JP-A-1998-306175, JP-A-1982-78431, JP-A-1979-157159, andJP-A-1980-13765. Specific examples of the phosphorous acid ester-basedstabilizer may include compounds as described below, but the phosphorousacid ester-based stabilizer capable of being used in the aspect of theinvention is not limited thereto.

It is more preferable that compounds disclosed in paragraphs [0023] to[0039] of JP-A-2004-182979 be used as the phosphorous acid-basedstabilizer. Specific examples of the phosphorous acid ester-basedstabilizer may include compounds disclosed in JP-A-1976-70316,JP-A-1998-306175, JP-A-1982-78431, JP-A-1979-157159, andJP-A-1980-13765. Other stabilizers may be preferably selected frommaterials disclosed in detail in pages 17 to 22 of the Journal ofTechnical Disclosure of Japan Institute of Invention and Innovation(Article No. 2001-1745, published on Mar. 15, 2001, Japan Institute ofInvention and Innovation).

As to examples thereof, ADK STAB 1178, ADK STAB 2112, ADK STAB PEP-8,ADK STAB PEP-24G, PEP-36G, and ADK STAB HP-10 of ADEKA CORPORATION, andSandostab P-EPQ of Clariant, Co. are placed on the market and can bepurchased. Additionally, it is preferable to use the stabilizer havingphenol and phosphorous acid ester in the same molecule. These compoundsand examples thereof are disclosed in detail in JP-A-1998-273494, butthe stabilizer capable of being used in the aspect of the invention isnot limited thereto. Examples of representative products that are placedon the market may include sumilizer GP of Sumitomo Chemical Co., Ltd.

(Thioether-Based Stabilizer)

The thioether-based stabilizer that is used as the stabilizer will bedescribed. According to the aspect of the invention, the thioether-basedstabilizer capable of being added to the cellulose acylate preferablyhas a molecular weight of 500 or more, and a known thioether-basedstabilizer may be used. Sumilizer TPL, sumilizer TPM, sumilizer TPS, andsumilizer TDP of Sumitomo Chemical Co., Ltd are placed on the market asthe thioether stabilizer. ADK STAB AO-412S of ADEKA CORPORATION iscapable of being purchased.

(Epoxy-Based Stabilizer)

It is preferable that the epoxy-based stabilizer contains an epoxycompound acting as an acid capture agent and disclosed in U.S. Pat. No.4,137,201. The epoxy compound which acts as the acid capture agent is anepoxy compound known in the related art, and examples thereof mayinclude epoxized vegetable oils and other unsaturated natural oils(these are usually called epoxized natural glyceride or unsaturatedfatty acid, and these fatty acids generally contain 12 to 22 carbonatoms) that are represented by compositions such as diglycidylethers ofvarious polyglycols, particularly polyglycols that are derived bycondensation of about 8 to 40 mole of ethylene oxide per 1 mole ofpolyglycol, diglycidylethers of glycerol, metal epoxy compounds (forexample, the matter that has been used in conjunction with a vinylchloride polymer composition in a vinyl chloride polymer composition),epoxized ether condensates, diglycidylethers of bisphenol A (that is,4,4′-dihydroxydiphenyldimethylmethane), epoxized unsaturated fatty acidesters (particularly, fatty acid having 2 to 22 carbon atoms, alkylesters having 4 to 2 carbon atoms (for example, butyl epoxy stearates)),and various epoxized long-chain fatty acid triglycerides (for example,epoxized soybean oil). Particularly preferable is an epoxide resincompound placed on the market that contains an epoxy group, that is,EPON 815c, or an epoxized ether oligomer condensate product.

A compound that has an aliphatic, aromatic, alicyclic, araliphatic, orheterocyclic structure and an epoxy group as a side chain is useful asthe epoxy-based stabilizer according to the aspect of the invention. Theepoxy group is preferably bonded to a residue of the molecule throughether or ester bonding using a glycidyl group, or is an N-glycidylderivative of heterocyclic amine, amide, or imide. These epoxy compoundsare extensively known, and capable of being easily purchased as productsplaced on the market. The materials of them are disclosed in detail inparagraphs [0096] to [0112] of JP-A-1999-189706.

More preferable is ET-4) epoxized linoleic acid octyl, ET-6) an epoxizedrecinoleic acid octyl, ET-7) epoxized soybean oil fatty acid octyl,ET-8) epoxized soybean oil, and ET-9) epoxized flaxseed oil, andparticularly preferably is ET-8) epoxized soybean oil or ET-9) epoxizedflaxseed oil. Examples of these epoxy-based materials may include ADKSTAB O-130P and ADK STAB O-180A (ADEKA CORPORATION), and the materialsare capable of being purchased as products placed on the market.

(Tin-Based Stabilizer)

A known tin-based stabilizer may be used as the tin-based stabilizer.Specific examples of the tin-based stabilizer may include an octyl tinmaleate polymer, monostearyl tin tris(isooctyl thioglycolate), anddibutyl tin dilaurate.

(Acid Capture Agent)

Since cellulose acylate is decomposed by acids at high temperatures, itis preferable that the optical film according to the aspect of theinvention contain the acid capture agent.

According to the aspect of the invention, any compound may be used as auseful acid capture agent as long as the compound is reacted with acidsto deactivate the acids. In connection with this, it is preferable thatthe compound has an epoxy group disclosed in U.S. Pat. No. 4,137,201.The epoxy compound which acts as the acid capture agent is an epoxycompound known in the related art, and examples thereof may includeepoxized vegetable oils and other unsaturated natural oils (these areusually called epoxized natural glyceride or unsaturated fatty acid, andthese fatty acids generally contain 12 to 22 carbon atoms) that arerepresented by compositions such as diglycidylethers of variouspolyglycols, particularly polyglycols that are derived by condensationof about 8 to 40 mole of ethylene oxide per 1 mole of polyglycol,diglycidylethers of glycerol, metal epoxy compounds (for example, thematter that has been used in conjunction with a vinyl chloride polymercomposition in a vinyl chloride polymer composition), epoxized ethercondensates, diglycidylethers of bisphenol A (that is,4,4′-dihydroxydiphenyldimethylmethane), epoxized unsaturated fatty acidesters (particularly, epoxized unsaturated fatty acid having 2 to 22carbon atoms, alkyl esters having 2 to 4 carbon atoms (for example,butyl epoxy stearates)), and various epoxized long-chain fatty acidtriglycerides (for example, epoxized soybean oil). Furthermore, it ispreferable to use EPON 815c as an epoxide resin compound placed on themarket that contains an epoxy group.

Examples of the acid capture agent that is capable of being used inaddition to the above-mentioned matters include oxetane compounds,oxazoline compounds, organic acid salts of alkaline earth metal,acetylacetonate complexes, and the matter disclosed in paragraphs 0068to 0105 of JP-A-1993-194788.

The acid capture agent is called an acid elimination agent, an acidcapture agent, an acid catcher, or the like, but there is no differencetherebetween in the aspect of the invention.

The acid capture agent of the material for forming the film used in theaspect of the invention may be one or more selected from theabove-mentioned examples, the addition amount of light stabilizer ispreferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, andparticularly preferably 0.01 to 2% by mass based on the mass of thecellulose acylate.

(Ultraviolet Absorbing Agent)

It is preferable that one or more ultraviolet absorbing agents becontained in cellulose-mixed ester according to the aspect of theinvention. It is preferable that the ultraviolet absorbing agent have anexcellent ultraviolet absorbing ability at a wavelength of 380 nm orless in views of deterioration prevention for liquid crystals and absorba small quantity of visible rays at a wavelength of 400 nm or more inviews of liquid crystal display property. Examples of the ultravioletabsorbing agent may include an oxybenzophenone-based compound, abenzotriazole-based compound, a salicylic acid ester-based compound, abenzophenone-based compound, a cyanoacrylate-based compound, a nickelcomplex-based compound, and the like. Particularly preferable examplesof the ultraviolet absorbing agent include the benzotriazole-basedcompound or the benzophenone-based compound. Among them, thebenzotriazole-based compound is preferable because of small unnecessarycoloring in respect to the cellulose-mixed ester. These are disclosed inJP-A-1985-235852, JP-A-1991-199201, JP-A-1993-1907073, JP-A-1993-194789,JP-A-1993-271471, JP-A-1994-107854, JP-A-1994-118233, JP-A-1994-148430,JP-A-1995-11056, JP-A-1995-11055, JP-A-1995-11056, JP-A-1996-29619,JP-A-1996-239509, and JP-A-2000-204173. The addition amount ispreferably 0.01 to 2% by mass of prepared melts and more preferably 0.01to 1.5% by mass.

Additionally, a polymer ultraviolet absorbing agent that is disclosed inJP-A-1994-148430 or a polymer containing ultraviolet absorbing agentmonomers may be used as the polymer ultraviolet absorbing agent that isavailable to the aspect of the invention without any limitation. Theweight average molecular weight of the polymer that is derived from theultraviolet absorbing monomers is preferably 2,000 to 30,000, and morepreferably 5,000 to 20,000. The amount of the ultraviolet absorbingmonomers in the polymer that is derived from the ultraviolet absorbingmonomers is preferably 1 to 70% by mass, and more preferably 5 to 60% bymass.

Examples of the ultraviolet absorbing agent monomer as the productavailable to the aspect of the invention include1-(2-benzotriazole)-2-hydroxy-5-(2-vinyloxycarbonylethyl)benzene,1-(2-benzotriazole)-2-hydroxy-5-(2-methacryroyloxyethyl)benzene ofreactive ultraviolet absorbing agent RUVA-93 that is the productmanufactured by Otsuka Chemical Holding Co., Ltd., or similar compoundsthereof. Preferably, a homopolymer, a copolymerized polymer, or acopolymer thereof may be used, but the aspect of the invention is notlimited thereto. For example, PUVA-30M that is manufactured by OtsukaChemical Holding Co., Ltd. is preferably used as a polymer ultravioletabsorbing agent which is the product placed on the market. Theultraviolet absorbing agents may be used in combination of two or morespecies thereof.

The following products placed on the market may be used as theultraviolet absorbing agent. Examples of benzotriazoles include TINUBINP (products manufactured by Ciba Specialty Chemicals, Inc.), TINUBIN 234(products manufactured by Ciba Specialty Chemicals, Inc.), TINUBIN 320(products manufactured by Ciba Specialty Chemicals, Inc.), TINUBIN 326(products manufactured by Ciba Specialty Chemicals, Inc.), TINUBIN 327(products manufactured by Ciba Specialty Chemicals, Inc.), TINUBIN 328(products manufactured by Ciba Specialty Chemicals, Inc.), sumisorb 340(products manufactured by Sumitomo Chemical Co., Ltd), and ADK STABLA-31 (ADEKA CORPORATION). Furthermore, examples of thebenzophenone-based ultraviolet absorbing agent may include seesorb100(products manufactured by SHIPROKASEI KAISYA, Ltd.), seesorb101(products manufactured by SHIPROKASEI KAISYA, Ltd.), seesorb101S(products manufactured by SHIPROKASEI KAISYA, Ltd.), seesorb102(products manufactured by SHIPROKASEI KAISYA, Ltd.), seesorb103(products manufactured by SHIPROKASEI KAISYA, Ltd.), ADK STAB LA-51(products manufactured by ADEKA CORPORATION), chemisorb111 (productsmanufactured by Chemipro Kasei Kaisha, Ltd.), UVINUL D-49 (productsmanufactured by BASF, Co), and the like. Furthermore, examples of theoxalic acid anilide-based ultraviolet absorbing agent include TINUBIN312 (products manufactured by Ciba Specialty Chemicals, Inc.) or TINUBIN315 (products manufactured by Ciba Specialty Chemicals, Inc.).Furthermore, examples of the salicylic acid-based ultraviolet absorbingagent include seesorb 201 (products manufactured by SHIPROKASEI KAISYA,Ltd.) or seesorb 202 (products manufactured by SHIPROKASEI KAISYA, Ltd.)as products placed on the market, and examples of thecyanoacrylate-based ultraviolet absorbing agent include seesorb 501(products manufactured by SHIPROKASEI KAISYA, Ltd.) and UVINUL N-539(products manufactured by BASF, Co.). Among them, particularlypreferable is ADK STAB LA-31.

The addition amount of the ultraviolet absorbing agent and theultraviolet absorbing polymer that are available to the aspect of theinvention depends on the type of compound and use conditions. However,in the case of the ultraviolet absorbing agent, the amount is preferably0.2 to 3.0 g per 1 m² of optical film, more preferably 0.4 to 2.0 g per1 m² of optical film, and particularly preferably 0.5 to 1.5 g per 1 m²of optical film. Furthermore, in the case of the ultraviolet absorbingpolymer, the amount is preferably 0.6 to 9.0 g per 1 m² of optical film,more preferably 1.2 to 6.0 g per 1 m² of optical film, and particularlypreferably 1.5 to 3.0 g per 1 m² of optical film.

(Hindered Amine Light Stabilizer)

Examples of the light stabilizer include the hindered amine lightstabilizer (HALS) compound which is a known compound, and examples ofthe hindered amine light stabilizer include 2,2,6,6-tetraalkylpiperidine compound, acid addition salts thereof, or complexes of themand metal compounds that are disclosed in paragraphs 5 to 11 of U.S.Pat. No. 4,619,956 and paragraphs 3 to 5 of U.S. Pat. No. 4,839,405.These are placed on the market as ADK STAB LA-57, ADK STAB LA-52, ADKSTAB LA-67, ADK STAB LA-62, and ADK STAB LA-77 of ADEKA CORPORATION, andTINUVIN 765 and TINUVIN 144 of Ciba Specialty Chemicals, Inc.

The hindered amine-based light resistant stabilizer may be used singlyor in combination of two or more species thereof. Furthermore, thehindered amine-based light resistant stabilizer may be used inconjunction with additives such as plasticizers, acid eliminationagents, and ultraviolet absorbing agents, or provided into a portion ofa molecular structure of each of the additives. The amount of additivesis appropriately selected within the range where an advantage of theinvention is not obstructed, but is preferably 0.01 to 20 parts by mass,more preferably 0.02 to 15 parts by mass, and particularly preferably0.05 to 10 parts by mass based on 100 parts by mass of the celluloseresin that is used in the aspect of the invention. These may be added atany step of the production process of melts, and the additives may beadded at the last step of the production process of melts.

In addition to the above-mentioned additives, various additives (forexample, an optical anisotropy controlling agent, microparticles, aninfrared absorbing agent, a surfactant, an odor trapping agent (amines,etc.), a thermal stabilizer, and the like) may be also added. For theinfrared absorbing dye, for example, matters described inJP-A-2001-194522 may be used. For the ultraviolet absorbing agent, forexample, matters described in JP-A-2001-151901 may be used. Each of themis preferably contained in an amount of 0.001 to 5% by mass with respectto the cellulose acylate. Microparticles preferably have an averageparticle size of 5 to 3000 nm, and may be formed of metal oxides orcrosslinked polymers. The microparticles are preferably contained in anamount of 0.001 to 5% by mass with respect to the cellulose acylate. Thedeterioration preventing agent is preferably contained in an amount of0.0001 to 2% by mass with respect to the cellulose acylate. The opticalanisotropy controlling agent may be exemplified by matters described inJP-A-2003-66230 and JP-A-2002-49128, and is preferably contained in anamount of 0.1 to 15% by mass with respect to the cellulose acylate.

(Pelletization)

The cellulose acylate and the additives are preferably mixed with eachother to be pelletized before the melt casting.

The cellulose acylate and the additives are melted at 150 to 250° C. byusing a twin screw or uniscrew kneading extruder and extruded to formnoodles, and the noodles are solidified in water and cut to perform thepelletization. The pelletization may be performed by using an underwatercut method in which extrusion and cutting are carried out in water. Itis more preferable that the pelletization be performed while pressure isreduced by using a vent type kneading extruder. Furthermore, it is morepreferable that the pelletization be performed while the inside of thekneading extruder is substituted by nitrogen.

As to the size of the preferable pellet, the sectional area is 1 to 300mm² and the length is 1 to 30 mm. More preferably, the sectional area is2 to 100 mm² and the length is 1.5 to 10 mm.

The number of rotations of the extruder is preferably 10 to 1000 rpm,and more preferably 30 to 500 rpm. The extrusion retention time of thepelletization is preferably 10 sec to 30 min and more preferably 30 secto 3 min.

(Specific Procedure of Melt Casting Method)

Hereinafter, the specific procedure of the melt casting method will bedescribed.

(1) Drying

Prior to the melt casting, the pellets are dried to remove watertherefrom, and the water content is adjusted to 0.1% by mass or less andmore preferably 0.01% by mass or less.

In order to achieve this, the drying temperature is preferably 40 to180° C., and the drying wind rate is preferably 20 to 400 m³/hour andmore preferably 100 to 250 m³/hour. The dew point of the drying wind ispreferably 0 to −60° C. and more preferably −20 to −40° C.

(2) Melt Extrusion

The dried cellulose acylate resin is supplied from a feed portion of anextruder into a cylinder.

A screw compression ratio of the extruder is preferably 2.5 to 4.5 andmore preferably 3.0 to 4.0. L (length of the screw)/D (diameter of thescrew) is preferably 20 to 70 and more preferably 24 to 50. Preferably,the melt temperature is as described above.

Full flight, Murdock, and Damage may be used as the screw.

In order to prevent oxidation of the resin, preferably, the inside ofthe extruder is substituted by an inert current (nitrogen and the like)or vacuum exhaustion is performed by using an extruder provided with avent.

(3) Filtration

Preferably, a breaker plate type of filtration is performed at an outletof the extruder.

In order to perform the high density filtration, the lip disk filtertype of filtration device is preferably provided after the resin passesthrough a gear pump. The filtration may be performed through a singlestage or multi stages. The filtration precision of the filtrationmaterial is preferably 3 to 15 μm and more preferably 3 to 10 μm.Stainless steel and steel are preferably used as the filtrationmaterial. Among them, stainless steel is preferable. A matter in whichwire rods are woven and a sintered metal filtration material may be usedas the filtration material, particularly, the latter is preferable.

(4) Gear Pump

In order to obtain an improvement in precision of the thickness (areduction in variation of the discharged amount), a gear pump ispreferably provided between the extruder and the dies. Thereby, avariation width in resin pressure of the die may be set to ±1% or less.

In order to improve an amount provision performance by using the gearpump, preferably, the number of rotations of the screw is changed and apressure before the gear pump is maintained. A high density gear pumpusing three or more gears is useful. Since retention in the gear pump isa factor of resin deterioration, it is preferable to form a structure inwhich the occurrence of retention is few. In order to stabilize anextrusion pressure, it is preferable to reduce a change in temperatureof an adaptor that connects the extruder and the gear pump or the gearpump and the die. Accordingly, it is more preferable to use an aluminuminjection heater.

(5) Die

If a design is performed so that the occurrence of retention of themolten resin is few in the die, any type of a T die, a fishtale die, anda hanger coat die may be used. Additionally, a static mixer may be addedimmediately before the T die in order to improve uniformity of the resintemperature. A clearance of the outlet portion of the T die is generally1.0 to 5.0 times as large as the thickness of the film and preferably1.3 to 2 times as large as the thickness of the film.

The clearance of the die is preferably controlled at the interval of 40to 50 mm, and more preferably at the interval of 25 mm or less.Furthermore, a process in which the thickness of the film of thedownstream is measured and feedback in respect to control of thicknessof the die is performed is useful to reduce a change in thickness.

In order to prepare a function layer at the outside layer, it ispossible to produce a film having a structure in which two or morespecies are provided by using a multilayered casting device.

After the resin is provided from the feed portion to the extruder, aretention time of the resin before the resin is discharged from the dieis preferably 2 to 60 min and more preferably 4 to 30 min.

(6) Cast

The molten resin that is extruded above a sheet so as to be higher thanthe die is cooled and solidified on a casting drum to obtain a film. Inconnection with this, it is preferable to use a touch roll.

The number of casting drums is preferably 1 to 8 and more preferably 2to 5, and it is preferable to perform slow cooling. The diameter of thecasting roll and the touch roll is preferably 50 to 5000 mm and morepreferably 150 to 1000 mm. As to the interval between a plurality ofcasting rolls, the interval in respect to face-to-face is preferably 0.3to 300 mm and more preferably 3 to 30 mm.

Next, peeling-off is performed in the casting drum, and the resultingsubstance passes through a nip roll and then wound. The thickness of theresulting film that is not stretched is preferably 30 to 400 μm and morepreferably 50 to 200 μm.

(7) Winding

It is preferable to perform trimming of both edges of the film beforethe winding is performed. A trimmed portion may be reused as a rawmaterial for films. Any one of a rotary cutter, a shear blade, and aknife may be used as the trimming cutter. As to the material, carbonsteel, stainless steel, or ceramic may be used. A winding tension ispreferably 1 to 50 kg/m width and more preferably 3 to 20 kg/m width. Inrespect to the winding tension, the winding may be performed with aconstant winding tension, but it is more preferable to perform thewinding while a taper is attached according to the winding diameter.

Furthermore, it is necessary to control a stretch ratio between niprolls and to prevent tension to the film in the line from beingincreased above a predetermined value. Before the winding, a laminatefilm may be attached to at least one side.

In the case of when the cellulose acylate composition of the aspect ofthe invention is a film, the amount of remaining organic solvent at thetime when the casting is performed is preferably 0.03% by mass or less,more preferably 0.02% by mass or less, and particularly preferably 0.01%by mass or less. In the case of when the remaining solvent is in theabove-mentioned range, desirably, it is difficult to generate an odor ofsolvent and to change physical properties of the film caused byvaporization of the solvent. The melt casting method is useful to reducethe amount of remaining solvent.

The amount of remaining solvent may be measured by using a gaschromatography method.

<Solution Casting>

Next, a preferred embodiment of the case of when cellulose acylate ofthe aspect of the invention is produced by using the solution castingmethod will be described.

In the aspect of the invention, a solvent of cellulose acylate is notlimited as long as cellulose acylate is capable of being dissolvedtherein and subjected to flow casting. Preferable examples of thesolvent may include a chlorine-based organic solvent such asdichloromethane, chloroform, 1,2-dichloroethane, andtetrachloroethylene, and a nonchlorine-based organic solvent.

Preferably, the nonchlorine-based organic solvent that is available tothe aspect of the invention is selected from ester, ketone, and etherhaving 3 to 12 carbon atoms. Ester, ketone, and ether may have a cyclicstructure. A compound that contains two or more of the functional groups(that is, —O—, —CO—, and —COO—) of ester, ketone, and ether may be usedas a main solvent, or the compound may have the different functionalgroup like an alcoholic hydroxyl group. In the case of the main solventhaving two or more functional groups, the number of carbon atoms may bewithin a predetermined range of the compound even though it has anyfunctional group. Examples of esters having 3 to 12 carbon atoms mayinclude ethyl formate, propyl formate, pentyl formate, methyl acetate,ethyl acetate, and pentyl acetate. Examples of ketones having 3 to 12carbon atoms may include aceton, methyl ethyl ketone, diethyl ketone,diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms mayinclude diisopropyl ether, dimethoxymethane, dimethoxyethane,1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole, and phenetole.Examples of the organic solvent having two or more functional groups mayinclude 2-ethoxyethyl acetate, 2-methoxy ethanol, and 2-buthoxy ethanol.

As to a nonchlorine-based organic solvent used in the aspect of theinvention, if cellulose acylate is capable of being dissolved thereinand subjected to flow casting, a chlorine-based organic solvent is notlimited. Preferable examples of the chlorine-based organic solvent mayinclude dichloromethane and chloroform. Particularly, dichloromethane ispreferable. Additionally, an organic solvent other than thechlorine-based organic solvent may be mixed. In this case, it isnecessary to use dichloromethane in an amount of at least 50% by mass.The nonchlorine-based organic solvent that is used in the aspect of theinvention will be described hereinafter. That is, preferably, thenonchlorine-based organic solvent is selected from ester, ketone, ether,alcohol, and hydrocarbon having 3 to 12 carbon atoms. Ester, ketone,ether, and alcohol may have a cyclic structure. A compound that containstwo or more of the functional groups (that is, —O—, —CO—, and —COO—) ofester, ketone, and ether may be used as a solvent, or the compound mayhave all the different functional groups like an alcoholic hydroxylgroup. In the case of the solvent having two or more functional groups,the number of carbon atoms may be within a predetermined range of thecompound even though it has any functional group. Examples of estershaving 3 to 12 carbon atoms may include ethyl formate, propyl formate,pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate.Examples of ketones having 3 to 12 carbon atoms may include aceton,methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone,cyclohexanone, and methyl cyclohexanone. Examples of ethers having 3 to12 carbon atoms may include diisopropyl ether, dimethoxymethane,dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole,and phenetole. Examples of the organic solvent having two or morefunctional groups may include 2-ethoxyethyl acetate, 2-methoxy ethanol,and 2-buthoxy ethanol.

Furthermore, alcohol that is used in conjunction with the chlorine-basedorganic solvent may have a straight chain, a branched chain, or a cyclicstructure. Among them, preferable is saturated aliphatic hydrocarbon.The hydroxyl group of alcohol may be any one of those of primary totertiary alcohols. Examples of alcohols include methanol, ethanol,1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol,2-methyl-2-butanol, and cyclohexanol. In addition, fluorine-basedalcohol may be used. For example, 2-fluoroethanol,2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol may be used.Additionally, hydrocarbons may have a straight chain, a branched chain,or a cyclic structure. Any one of aromatic hydrocarbons and aliphatichydrocarbons may be used. The aliphatic hydrocarbons may be saturated orunsaturated. Examples of the hydrocarbons include cyclohexane, hexane,benzene, toluene, and xylene.

Examples of the nonchlorine-based organic solvent that is used inconjunction with the chlorine-based organic solvent as the main solventapplied to the cellulose acylate include, but are not limited to methylacetate, ethyl acetate, methyl formate, ethyl formate, aceton, dioxolan,dioxane, ketones or ester acetates having 4 to 7 carbon atoms, oralcohols or hydrocarbons having 1 to 10 carbon atoms. Furthermore,preferable examples of the nonchlorine-based organic solvent may includemethyl acetate, aceton, methyl formate, ethyl formate, methyl ethylketone, cyclopentanon, cyclohexanon, acetyl methyl acetate, methanol,ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, cyclohexanol,cyclohexane, and hexane.

It is preferable that the cellulose acylate according to the aspect ofthe invention be dissolved in the organic solvent in an amount of 10 to35% by mass. In the cellulose acylate solution, the amount is morepreferably 13 to 30% by mass and particularly preferably 15 to 28% bymass. In order to dissolve the cellulose acylate at the above-mentionedconcentration, the dissolution may be performed so that a predeterminedconcentration is ensured at the dissolution step, or a solution having alow concentration (for example, 9 to 14% by mass) is prepared in advanceand then concentrated so that a predetermined high concentrationsolution is obtained during the concentration process as describedbelow. Alternatively, after the cellulose acylate solution having thehigh concentration is prepared in advance, various types of additivesmay be added to produce the cellulose acylate solution having apredetermined low concentration. Any method of the above-mentionedmethods may be used as long as the desired concentration of thecellulose acylate solution according to the aspect of the invention isobtained.

As to the preparation of the cellulose acylate solution (dope) accordingto the aspect of the invention, the dissolution method is not limitedand may be performed at room temperature. Additionally, the dissolutionmay be performed by using a cooling dissolution method, a hightemperature dissolution method, or a combination thereof. With respectto this, a method of preparing a cellulose acylate solution is disclosedin, for example, JP-A-1993-163301, JP-A-1986-106628, JP-A-1983-127737,JP-A-1997-95544, JP-A-1998-95854, JP-A-1998-45950, JP-A-2000-53784,JP-A-1999-322946, JP-A-1999-322947, JP-A-1990-276830, JP-A-2000-273239,JP-A-1999-71463, JP-A-1992-259511, JP-A-2000-273184, JP-A-1999-323017,and JP-A-1999-302388. As to the above-mentioned dissolution methods ofcellulose acylate to the organic solvent, if the methods are in thedesirable range of the aspect of the invention, they can be used. Inrespect to details thereof, particularly, details of thenonchlorine-based solvent system, the method that is disclosed in detailin the Journal of Technical Disclosure of Japan Institute of Inventionand Innovation (Article No. 2001-1745, published on Mar. 15, 2001, pages22 to 25, Japan Institute of Invention and Innovation) is performed. Inaddition, the cellulose acylate solution according to the aspect of theinvention is generally subjected to solution concentration andfiltration, and is described in detail in the Journal of TechnicalDisclosure of Japan Institute of Invention and Innovation (Article No.2001-1745, published on Mar. 15, 2001, page 25, Japan Institute ofInvention and Innovation). Additionally, in the case of when thedissolution is performed at high temperatures, the temperature isgenerally the boiling point of the used organic solvent or higher. Inthis case, the dissolution is performed while pressure is applied.

In respect to the cellulose acylate solution according to the aspect ofthe invention, it is preferable that viscosity and kinetic storageelasticity of the solution be within a predetermined range. 1 mL ofsample solution is analyzed by using a rheometer (CLS 500) and a steelcone having a diameter of 4 cm/2° (all of them are products manufacturedby TA Instruments, Co.). As to the analysis conditions, the analysis isperformed while an oscillation step/temperature ramp is 2° C./min inrespect to the range of 40 to −10° C., and static non-Newtonianviscosity n*(Pa·s) at 40° C. and storage elasticity G′ (Pa) at −5° C.are obtained. Furthermore, after the temperature of the sample solutionis maintained until the temperature of liquid is made constant at ananalysis initiation temperature, the analysis starts to be performed. Inthe aspect of the invention, preferably, the viscosity at 40° C. is 1 to400 Pa·s and dynamic storage elasticity at 15° C. is 500 Pa or more.More preferably, the viscosity at 40° C. is 10 to 200 Pa·s and dynamicstorage elasticity at 15° C. is 100 to 1,000,000 Pa. In addition, it ispreferable that the dynamic storage elasticity be as high as possible atlow temperatures. For example, in the case of when the flow castingsupport is at −5° C., it is preferable that the dynamic storageelasticity be 10,000 to 1,000,000 Pa at −5° C. In the case of when thesupport is at −50° C., it is preferable that the dynamic storageelasticity be 10,000 to 5,000,000 Pa at −50° C.

(Specific Procedure of Solution Casting)

Next, a method for producing a cellulose acylate film according to theaspect of the invention will be described. As to the method and thedevice for producing the cellulose acylate film according to the aspectof the invention, a solution flow casting method and a solution flowcasting device that are used to produce a known cellulose acylate filmare used. A dope (cellulose acylate solution) that is prepared in adissolution device (pot) is stored in a storage pot to remove bubblesfrom the dope, thereby achieving final preparation. The dope isdischarged from a dope discharge portion through a pressure quantitativegear pump that is capable of performing quantitative analysis andtransporting liquid with high precision by using the number of rotationsto a pressure die. The dope is uniformly flow cast from a nozzle of apressure die (slit) onto a metal support of a flow casting portion thatis endlessly operated, so that a dope layer (this is usually called web)which is insufficiently dried is peeled off from the metal support at apeeling point where the metal support almost circuits. Both edges of theobtained web are fixed by using clips, transported by using a tenterwhile its width is maintained, dried, transported to a group of rolls ofa dryer to finish the drying, and wound by using a winding machine so asto ensure a predetermined length. The combination of the tenter and agroup of rolls of the dryer depends on the purpose. In the solution flowcasting method that is applied to halogenated silver photosensitivephoto materials or functional films for protecting electronic displays,in addition to the solution flow casting device, a coating device isfrequently provided to perform surface treatment in respect to filmssuch as a under coat layer, a charge prevention layer, a halationprevention layer, and a protective layer. Production processes inrespect to them are disclosed in detail in the Journal of TechnicalDisclosure of Japan Institute of Invention and Innovation (Article No.2001-1745, published on Mar. 15, 2001, pages 25 to 30, Japan Instituteof Invention and Innovation) is performed, and are classified into flowcasting (cocasting is contained), metal supports, drying, peeling,stretching, and the like.

In the aspect of the invention, a space temperature of a flow castingportion is not limited, but preferably −50 to 50° C., more preferably−30 to 40° C., and particularly preferably −20 to 30° C. Particularly,the cellulose acylate solution that is flow cast at the low spacetemperature is instantaneously cooled on the support to improve a gelstrength, thereby forming the film that contains the organic solvent.Therefore, the peeling from the support may be performed for a shorttime while the organic solvent is not vaporized from the celluloseacylate, and high-speed flow casting may be achieved. Furthermore, air,nitrogen, argon, helium, or the like may be used as means for coolingthe space, and the type of means is not limited. In this case, therelative humidity is preferably 0 to 70% and more preferably 0 to 50%.Furthermore, in the aspect of the invention, the temperature of thesupport of the flow casting portion in which the cellulose acylatesolution is flow cast is −50 to 130° C., preferably −30 to 25° C., andmore preferably −20 to 15° C. In order to maintain the flow castingportion at the temperature of the aspect of the invention, cooled gasmay be supplied to the flow casting portion or the space may be cooledby disposing a cooling device at the flow casting portion. In connectionwith this, it is necessary to prevent water from being attached, and amethod using dry gas may be performed.

According to the aspect of the invention, in respect to the contents andthe flow casting of the layers, the following configuration ispreferable. That is, preferably, the cellulose acylate solution is acellulose acylate solution that contains at least one plasticizer ofliquid or solid at 25° C. in an amount of 0.1 to 20% by mass based oncellulose acylate, a cellulose acylate solution that contains at leastone ultraviolet absorbing agent of liquid or solid in an amount of 0.001to 5% by mass based on cellulose acylate, a cellulose acylate solutionthat contains at least one solid including fine particles having anaverage particle size of 5 to 3000 nm in an amount of 0.001 to 5% bymass based on cellulose acylate, a cellulose acylate solution thatcontains at least one fluorine-based surfactant in an amount of 0.001 to2% by mass based on cellulose acylate, a cellulose acylate solution thatcontains at least one peeling agent in an amount of 0.0001 to 2% by massbased on cellulose acylate, a cellulose acylate solution that containsat least one deterioration prevention agent in an amount of 0.0001 to 2%by mass based on cellulose acylate, a cellulose acylate solution thatcontains at least one optical anisotropic control agent in an amount of0.1 to 15% by mass based on cellulose acylate, and/or a celluloseacylate solution that contains at least one infrared absorbing agent inan amount of 0.1 to 5% by mass based on cellulose acylate, and it ispreferable that the cellulose acylate film be produced using theabove-mentioned cellulose acylate solution.

During the flow casting process, one type of cellulose acylate solutionmay be subjected to single layer flow casting, or two or more types ofcellulose acylate solutions may be subjected to cocasting simultaneouslyor sequentially. In the case of when flow casting of two or more layersare performed, in respect to the produced cellulose acylate solution andthe cellulose acylate film that is produced by using the celluloseacylate solution, preferably, chlorine-based solvent compositions of thelayers are the same as each other or different from each other,additives of the layers are one type or a mixture containing two or moretypes, the additives of the layers are added to the same layer or thedifferent layers, concentrations of the solutions of the additives arethe same as each other or different from each other in respect to thelayers, molecular weights of associates of the layers are the same aseach other or different from each other, temperatures of the solutionsof the layers are the same as each other or different from each other,coating amounts of the layers are the same as each other or differentfrom each other, viscosities of the layers are the same as each other ordifferent from each other, film thicknesses of the layers after thedrying are the same as each other or different from each other,materials of the layers are on the same state or distribution ordifferent states or distributions, physical properties of the layers arethe same as each other or different from each other, or the physicalproperties of the layers are on the same physical property distributionor different physical property distributions. In connection with this,the physical properties include physical properties that are disclosedin detail in the Journal of Technical Disclosure of Japan Institute ofInvention and Innovation (Article No. 2001-1745, published on Mar. 15,2001, pages 6 and 7, Japan Institute of Invention and Innovation).Examples thereof include haze, permeability, spectral properties,retardation Re, retardation Rth, molecular alignment axis, axialmisalignment, tearing strength, folding strength, tensile strength, adifference in inner and outer Rts of wound matters, creaking, dynamicfriction, alkaline hydrolysis, curl values, water content, remainingsolvent amounts, thermal shrinkage, high humidity dimension evaluation,water vapor permeation, flatness of bases, dimensional stability,thermal shrinking initiation temperatures, elasticity, observance ofbright impurity, impedance that is used to evaluate bases, and surfacestates. Furthermore, a yellow index, transparency, and thermal physicalproperties (Tg and crystallization heat) of the cellulose acylate thatare disclosed in detail in the Journal of Technical Disclosure of JapanInstitute of Invention and Innovation (Article No. 2001-1745, publishedon Mar. 15, 2001, page 11, Japan Institute of Invention and Innovation)may be included.

<Treatment of the Cellulose Acylate Film>

(Stretching)

The cellulose acylate film that is produced by using the melt castingmethod or the solution casting method is preferably stretched in orderto improve the surface shape, ensure desirable Re and Rth, and improvelinear expansibility.

The stretching may be carried out on-line during the casting process ormay be carried out off-line after the cellulose acylate film is wound-uponce after completion of the casting. That is, in the case of when themelt casting is performed, the stretching may be performed while thecooling is not finished during the casting process or after the coolingis finished.

The above stretching may be carried out at temperature in the range ofpreferably from Tg to (Tg+50° C.), more preferably from (Tg+1° C.) to(Tg+30° C.), and particularly preferably from (Tg+2° C.) to (Tg+20° C.).A stretching ratio may be preferably from 0.1 to 500%, more preferablyfrom 10 to 300%, and particularly preferably from 30 to 200%. Thestretching may be carried out in a single step or multiple steps. Thestretching ratio herein used is defined as described below:Stretch ratio (%)=100×{(length after stretching)−(length beforestretching)}/(length before stretching).

Such stretching may be achieved by lengthwise stretching, crosswisestretching, and a combination thereof. The lengthwise stretching mayinclude (1) roll stretching (stretching which is performed in thedirection of the length by the use of two or more pairs of nip roles,the rim speed at the outlet of which is higher) and (2) fixed stagestretching (stretching which is performed in the direction of the lengthby increasingly rapidly transporting the film in a length directionwhile both edges of the film are held). Furthermore, the crosswisestretching may include a tenter stretching (stretching in which bothedges of a film are grasped by a chuck and extended to crosswisedirection (the direction perpendicular to lengthwise direction)). Thelengthwise stretching and the crosswise direction may be performedseparately (uniaxial stretching) or in a combination thereof (biaxialstretching). In the case of when the biaxial stretching is performed,the lengthwise stretching and the crosswise stretching may besequentially performed (sequential stretching) or simultaneouslyperformed (simultaneous stretching).

The stretching speeds of the lengthwise stretching and the crosswisestretching are preferably from 10%/minute to 10000%/minute, morepreferably from 20%/minute to 1000%/minute, and particularly preferablyfrom 30%/minute to 800%/minute. In the case of when the multistepstretching is performed, an average value of the stretching speeds ofthe steps is used.

After the stretching, it is preferable that lengthwise or crosswiserelaxation be performed by 0 to 10%. Furthermore, after the stretching,it is preferable to perform heat fixing at 150 to 250° C. for 1 sec to 3min.

After the stretching, the film thickness is preferably 10 to 300 μm,more preferably 20 to 200 μm, and particularly preferably 30 to 100 μm.

An angle (θ) which the direction of casting (lengthwise direction) formswith a retardation axis of Re of a film is preferably as closer aspossible to 0°, +90°, or −90°. That is to say, in the case of thelengthwise stretching, it is preferably as closer as possible to 0°,more preferably 0±3°, even more preferably 0±2°, and particularlypreferably 0±1°. In the case of the crosswise stretching, it ispreferably 90±3° or −90±3°, more preferably 90±2° or −90±2°, andparticularly preferably 90±1° or −90±1°.

The unstretched or stretched cellulose acylate film may be used alone orin conjunction with a polarizing plate, and a liquid crystal layer, alayer that has a controlled refractive index (low reflective layer), ora hard coating layer may be provided thereon.

(Photoelasticity)

The cellulose acylate film that is obtained by using the productionmethod according to the aspect of the invention is preferably used as aprotective film of a polarizing plate or a retardation film. In the caseof when the cellulose acylate film is used as the protective film of thepolarizing plate or the retardation film, birefringence (Re and Rth) maybe changed due to stress caused by stretching and shrinkage due tomoisture absorption. The change of the birefringence according to thestress may be measured by using the photoelasticity.

The photoelasticity is preferably 5×10⁻⁷ (cm²/kgf) to 30×10⁻⁷ (cm²/kgf),more preferably 6×10⁻⁷ (cm²/kgf) to 25×10⁻⁷ (cm²/kgf), and particularlypreferably 7×10⁻⁷ (cm²/kgf) to 20×10⁻⁷ (cm²/kgf).

(Surface Treatment)

An unstretched or stretched cellulose acylate film may be subjected to asurface treatment, if necessary, in order to improve adhesion strengthbetween the cellulose acylate film and each functional layer (e.g.,undercoat layer and back layer). For example, a glow dischargetreatment, an ultraviolet ray treatment, a corona treatment, a flametreatment, an acid treatment, or an alkali treatment may be applied. Theglow discharge treatment referred to herein may be a treatment withlow-temperature plasma performed in a low-pressure gas at a pressure of10⁻³ to 20 Torr or preferably with plasma at the atmospheric pressure. Aplasma excitation gas is a gas which can be excited to plasma underconditions as described above, and examples thereof include argon,helium, neon, krypton, xenon, nitrogen, carbon dioxide,chlorofluorocarbons such as tetrafluoromethane, and a mixture thereof.Details thereof are described in the Journal of Technical Disclosure ofJapan Institute of Invention and Innovation (Article No. 2001-1745,published on Mar. 15, 2001, pages 30 to 32, Japan Institute of Inventionand Innovation). In the plasma treatment at the atmospheric pressure, towhich attention has been paid in recent years, for example, a radiatingenergy of 20 to 500 kgy is used under a condition of 10 to 1,000 keV,and preferably a radiating energy of 20 to 300 kgy is used under acondition of 30 to 500 keV. Of these treatments, an alkali saponifyingtreatment is particularly preferable, which treatment is very useful toperform the surface treatment for cellulose acylate film.

The alkali saponifying treatment may be conducted by immersing the filminto a saponifying solution, or applying a saponifying solution onto thefilm. In the case of the immersing method, the treatment can be attainedby passing the film into a tank wherein an aqueous solution of NaOH,KOH, or the like which has a pH of 10 to 14 and is heated to 20 to 80°C., is put for 0.1 to 10 minutes, neutralizing the solution on the film,washing the film, and drying the film.

Examples of the application method may include dip coating, curtaincoating, extrusion coating, bar coating, and E type coating. As thesolvent in the alkali saponifying treatment coating solution, it ispreferable to employ a solvent which has an excellent wettabilityappropriate for applying the saponifying solution to a support and canhold favorable surface conditions without forming any irregularity onthe support surface. More specifically speaking, it is preferable to usean alcoholic solvent, and particularly preferably isopropyl alcohol. Itis also possible to employ an aqueous solution of a surfactant as thesolvent. As the alkali in the liquid saponifying solution, it ispreferable to use an alkali soluble in the above-described solvent, andKOH and NaOH are still preferable. It is preferable that the liquidsaponifying agent have a pH value of 10 or more, still preferably 12 ormore. Concerning the reaction conditions during the alkalisaponification, it is preferable to perform the saponification at roomtemperature for 1 sec to 5 minutes, still preferably for 5 seconds to 5minutes, and particularly preferably for 20 seconds to 3 minutes. Afterthe completion of the alkali saponification reaction, it is preferableto wash the face coated with the liquid saponifying agent by using wateror by using an acid and then water. The solution-applying mannersaponifying treatment, and the application of an alignment film, whichwill be detailed later, may be continuously conducted. In the case, thenumber of steps can be reduced. These saponifying methods arespecifically described in, for example, JP-A-2002-82226 and WO 02/46809.

It is preferable to form an undercoat layer on the film in order to bondthe film to a functional layer. This layer may be applied onto the filmafter the above-mentioned surface treatment is conducted, or withoutconducting any surface treatment. Details of the undercoat layer aredescribed in the Journal of Technical Disclosure of Japan Institute ofInvention and Innovation (Article No. 2001-1745, published on Mar. 15,2001, page 32, Japan Institute of Invention and Innovation).

The surface treatment and the priming process may be integrated, as afinal stage, into the casting process, or may be carried outindependently or in the middle of the process of providing thefunctional layer, which will be detailed just below.

<Combination with the Functional Layer>

The cellulose acylate film according to the aspect of the invention maybe combined with the functional layers, details of which are describedin the Journal of Technical Disclosure of Japan Institute of Inventionand Innovation (Article No. 2001-1745, published on Mar. 15, 2001, pages32 to 45, Japan Institute of Invention and Innovation). Among thesefunctional layers, preferable are provision of a polarizing film(formation of a polarizing plate), provision of an opticallycompensating layer (an optically compensating sheet), and provision ofan antireflection layer (an antireflection film).

[Polarizing Film]

(Material of the Polarizing Film)

At present, a commercially available polarizing film may be generallyformed by immersing a stretched polymer into a solution of iodine or adichroic dye in a bath, thereby causing the iodine or dichroic dye topermeate the binder. As the polarizing film, a coating type polarizingfilm, typical examples of which are manufactured by Optiva Inc., mayalso be used.

The iodine and the dichroic dye in the polarizing film are aligned inthe binder, thereby exhibiting polarizing performance. Examples ofdichroic dyes include azo series dyes, stilbene series dyes, pyrazoloneseries dyes, triphenylmethane series dyes, quinoline series dyes,oxazine series dyes, thiazine series dyes, and anthraquinone seriesdyes. Of these dyes, water-soluble dyes are preferred. The dichroic dyespreferably contain hydrophilic substituent (for example, sulfo, amino,and hydroxyl groups). Examples thereof may include compounds describedin the Journal of Technical Disclosure of Japan Institute of Inventionand Innovation (Article No. 2001-1745, page 58, published on Mar. 15,2001, Japan Institute of Invention and Innovation).

The binders of the polarizing film may be polymers capable ofcross-linking by themselves, polymers capable of undergoingcross-linking reaction in the presence of a cross-linking agent, orcombinations thereof. Examples of these binders includemethacrylate-based copolymers, styrene-based copolymers, polyolefins,polyvinyl alcohols and modified polyvinyl alcohols,poly(N-methylolacrylamides), polyesters, polyimides, vinyl acetatecopolymers, carboxymethyl celluloses, polycarbonates, and the likedescribed in paragraph [0022] of the specification in JP-A-1996-338913.A silane coupling agent may be used as a polymer.

Of them, the water-soluble polymers (for example,poly(N-methylolacrylamides), carboxymethyl celluloses, gelatin,polyvinyl alcohols and modified polyvinyl alcohols) are preferable,gelatin, and polyvinyl alcohols and modified polyvinyl alcohols are morepreferable, polyvinyl alcohols and modified polyvinyl alcohols areparticularly preferable. It is particularly preferable to use two typesof polyvinyl alcohols or modified polyvinyl alcohols having differentpolymerization degrees. Polyvinyl alcohols usable in the invention havea saponification degree in the range of preferably 70 to 100% and morepreferably 80 to 100%.

The polymerization degree of the polyvinyl alcohols is preferably from100 to 5,000.

With regard to modified polyvinyl alcohols, they are disclosed inJP-A-1996-338913, JP-A-1997-152509, and JP-A-1997-316127. Two or moretypes of polyvinyl alcohols and modified polyvinyl alcohols may be usedtogether.

It is preferable that the lower limit of the thickness of the binder be10 μm. The upper limit of the thickness is preferably as small aspossible in the views of light leakage from the liquid crystal displaydevice. The thickness is preferably the same as that (about 30 μm) ofpolarizing plates commercially available at the present or lower thanthat, is more preferably 25 μm or less, and particularly preferably 20μm or less.

The binder in the polarizing film may be crosslinked. A polymer ormonomer having a crosslinkable functional group may be incorporated intothe binder, or a crosslinkable functional group may be given to thebinder polymer itself. The crosslinking may be attained by light, heat,or pH change, so as to make it possible to cause the binder to have acrosslinked structure. Crosslinking agents are disclosed in U.S. Pat.Re-issue No. 23297. A boron compound (for example, boric acid or borax)may also be used as a crosslinking agent. The amount of the crosslinkingagent added to the binder is preferably from 0.1 to 20 wt % based on thebinder. In this case, the alignment of the polarizer and the wet heatresistance of the polarizing film become good.

After the end of the crosslinking reaction, the amount of thecrosslinking agent which has not reacted is preferably 1.0% by mass orless and more preferably 0.5% by mass or less. Thereby, the weatherresistance of the film is improved.

(Stretching of the Polarizing Film)

It is preferable that the polarizing film be stretched (stretchingprocess) or be rubbed (rubbing process) and then dyed with iodine or adichroic dye.

In the case of the stretching process, the stretch ratio is preferably2.5 to 30.0 and more preferably 3.0 to 10.0. The stretching may becarried out by dry stretching in the air. Alternatively, wet stretchingmay be performed while the film is immersed in water. The stretch ratioof the dry stretching is preferably from 2.5 to 5.0, and the stretchratio of the wet stretching is preferably from 3.0 to 10.0. The stretchratio means a ratio of the length of the polarizing film after thestretching/the length of the polarizing film before the stretching. Thestretching may be performed in parallel to the MD direction (parallelstretching), or obliquely (oblique stretching). The stretching may beattained by one stretching operation or plural stretching operations.The stretching based on the plural stretching operations makes itpossible to stretch the uniformly even when a high-ratio stretching isperformed. More preferable is oblique stretching where the film isstretched at an angle of 10 to 80° oblique to the film-carrieddirection.

(1) Parallel Stretching Process

Before the film is stretched, the PVA film is swelled. The swellingdegree thereof (the mass ratio of the film before the swelling to thefilm after the swelling) is generally 1.2 to 2.0. Thereafter, while thefilm may be continuously transported through guide rolls and the like,the film is stretched in an aqueous medium bath or a dyeing bath where adichroic material is dissolved at a bath temperature of generally 15 to50° C., and preferably 17 to 40° C. The stretching may be attained bygrasping the film by means of two pairs of nip rolls, the transportationrate of the backward nip rolls being made larger than that of theforward nip rolls. The stretch ratio (the ratio of the length of thestretched film to that of the film at the initial stage: identicalwording thereafter), is preferably 1.2 to 3.5, and more preferably 1.5to 3.0 from the viewpoint of the above-mentioned effects. Thereafter,the film is dried at 50 to 90° C. to obtain a polarizing film.

(2) Oblique Stretching Process

As this process, a method described in JP-A-2002-86554 may be usedwherein a tenter projected in an oblique direction is used to performstretching. Since this stretching is performed in the air, it isnecessary to hydrate the film beforehand so as to be made easy tostretch. The water content in the film is preferably 5 to 100%, and morepreferably 10 to 100%.

The temperature when the film is stretched is preferably 40 to 90° C.,and more preferably from 50 to 80° C. The relative humidity ispreferably 50 to 100%, more preferably 70 to 100%, and particularlypreferably 80 to 100%. The advance speed in the longitudinal directionis preferably 1 m/minute or more, and more preferably 3 m/minute ormore.

After the end of the stretching, the film is dried at preferably 50 to100° C. and more preferably 60 to 90° C. for preferably 0.5 to 10minutes and more preferably 1 to 5 minutes.

The angle of the absorption axis of the thus-obtained polarizing film ispreferably 10 to 800, and more preferably 30 to 60°, and substantiallyparticularly preferably 45° (40 to 500).

[Adhesion]

The saponified cellulose acylate film and the polarizing layer preparedby the stretching may be adhered to each other to prepare a polarizingplate. About the direction along which they are adhered to each other,the angle between the directions of the flow casting axis of thecellulose acylate film and the stretch axis of the polarizing plate ispreferably set to 45°.

The adhesive agent for the adhesion is not particularly limited.Examples thereof include PVA-based resins (comprising modified PVA whichmodified with an acetoacetyl, sulfonic acid, carboxyl, oxyalkylene orsome other group) or an aqueous solution of a boron compound. Amongthem, the PVA-based resins are preferable. The thickness of the adhesiveagent layer is preferably 0.01 to 10 μm, and more preferably 0.05 to 5μm after the layer is dried.

It is preferable that the light permeability of the thus-obtainedpolarizing plate be higher and the polarization degree thereof behigher. The permeability of the polarizing plate in respect to lighthaving a wavelength of 550 nm is preferably 30 to 50%, more preferably35 to 50%, and particularly preferably 40 to 50%. The polarizationdegree thereof to light having a wavelength of 550 nm is preferably 90to 100%, more preferably 95 to 100%, and particularly preferably 99 to100%.

The thus-obtained polarizing plate is laminated on a λ/4 plate, wherebya circular polarization plate can be produced. In this case, thelaminating is carried out to set the angle between the retardation axisof the λ/4 plate and the absorption axis of the polarizing plate to 45°.At this time, the λ/4 plate is not particularly limited, and ispreferably a λ/4 plate having a wavelength dependency such that theretardation thereof is smaller to a lower wavelength. It is alsopreferable to use a λ/4 plate composed of a polarizing film having anabsorption axis inclined at an angle of 20 to 70° to the longitudinaldirection and an optically anisotropic layer made of a liquid crystalcompound.

[Provision of an Optically Compensating Layer (Production of anOptically Compensating Sheet)]

The optically anisotropic layer is a layer for making compensation for aliquid crystal compound in a liquid crystal cell in a liquid crystaldisplay device at the time of black display, and is provided by formingan alignment film on cellulose acylate film and further forming anoptically anisotropic layer thereon.

(Alignment Film)

An alignment film is provided on the above-mentioned surface-treatedcellulose acylate film. This film has a function of deciding thealignment direction of liquid crystal molecules. However, if a liquidcrystal compound is aligned and subsequently the alignment state isfixed, the alignment film is not essential as a constituent elementsince the alignment film has fulfilled the function thereof. In otherwords, only the optically anisotropic layer which is in a fixedalignment state and is formed on the alignment film is transferred ontoa polarizer, whereby the polarizing plate using cellulose acylate filmaccording to the aspect of the invention can be produced.

The alignment film may be provided by rubbing an organic compound(preferably a polymer), performing oblique evaporation of an inorganiccompound, forming a layer having a micro groove, or performingaccumulation of an organic compound (for example, ω-tricosanoic acid,dioctadecylmethylammonium chloride or methyl stearate) by theLangmuir-Blodgett method (LB film). Furthermore, there have been knownalignment films having an alignment function imparted thereto byapplying an electrical field or a magnetic field, or radiating light.

It is preferable to form the alignment film by performing rubbingtreatment of a polymer. In principle, the polymer used in the alignmentfilm has a molecular structure having a function of aligning liquidcrystal molecules.

According to the aspect of the invention, it is preferable to not onlycause the polymer used in the alignment film to have the above-mentionedfunction of aligning liquid crystal molecules, but also introduce, intothe main chain of the polymer, a side chain having a crosslinkablefunctional group (for example, a double bond), or it is preferable tointroduce, into a side chain of the polymer, a crosslinkable functionalgroup having a function of aligning liquid crystal molecules.

The polymers used in the alignment film may be polymers capable ofcross-linking by themselves, polymers capable of undergoingcross-linking reaction in the presence of a cross-linking agent, orcombinations thereof. Examples of the polymers includemethacrylate-based copolymers described in paragraph [0022] of thespecification in JP-A-1996-338913, styrene-based copolymers,polyolefins, polyvinyl alcohols and modified polyvinyl alcohols,poly(N-methylolacrylamides), polyesters, polyimides, vinyl acetatecopolymers, carboxymethyl celluloses, polycarbonates, and the like. Asilane coupling agent may be used as a polymer. Water-soluble polymers(for example, poly(N-methylolacrylamides), carboxymethyl celluloses,gelatin, and polyvinyl alcohols or modified polyvinyl alcohols) arepreferable. Gelatin, polyvinyl alcohols, and modified polyvinyl alcoholsare more preferable, polyvinyl alcohols and modified polyvinyl alcoholsare even more preferable. It is particularly preferable to use two typesof polyvinyl alcohols or modified polyvinyl alcohols having differentpolymerization degrees. Polyvinyl alcohols have a saponification degreein the range of, preferably 70 to 100%, and more preferably 80 to 100%.It is preferable that the polymerization degree of polyvinyl alcohols be100 to 5000.

The side chain having a function of aligning liquid crystal moleculesgenerally has a hydrophobic group as a functional group. Specifically,the type of functional group depends on the type of the liquid crystalmolecule and a required alignment state.

For example, the modifying groups of the modified polyvinyl alcohol maybe introduced by copolymerization modification, chain transfermodification, and block polymerization modification. Examples of themodifying groups may include hydrophilic groups (carboxylic acid group,sulfonic acid group, phosphonic acid group, amino group, ammonium group,amide group, thiol group, and the like), a hydrocarbon group having 10to 100 carbon atoms, a fluorine atom-substituted hydrocarbon group, athioether group, a polymerizable group (unsaturated polymerizable group,epoxy group, aziridinyl group, and the like), and an alkoxysilyl group(trialkoxysilyl group, dialkoxy group, monoalkoxy group, and the like).Examples of the modified polyvinyl alcohol compounds are disclosed inparagraphs [0022] to [0145] of JP-A-2000-155216 and paragraphs [0018] to[0022] of JP-A-2002-62426.

When a side chain having a crosslinkable functional group is bonded tothe main chain of the aligned film polymer or a crosslinkable functionalgroup is introduced into a side chain thereof having a function ofaligning liquid crystal molecules, the aligned film polymer may becopolymerized in conjunction with a polyfunctional monomer contained inthe optically anisotropic layer. As a result, strong bonding is attainedby covalent bonds between the polyfunctional monomers, between thealigned film polymers, and between the polyfunctional monomers and thealigned film polymers. Consequently, the introduction of thecrosslinkable functional group into the aligned film polymer makes itpossible to improve the strength of the optically compensating sheetremarkably.

The crosslinkable functional group of the aligned film polymerpreferably contains a polymerizable group in the same manner as thepolyfunctional monomer. Specific examples thereof are described inparagraphs [0080] to [0100] of JP-A-2000-155216. The aligned filmpolymer may be crosslinked with a crosslinking agent, separately inrespect to the above-mentioned crosslinkable functional group.

Examples of the crosslinking agent include aldehydes, N-methylolcompounds, dioxane derivatives, compounds that works when the carboxylicgroup is activated, active vinyl compounds, active halogen compounds,isooxazoles, and dialdehyde starch. Two or more crosslinking agents maybe used in combination. Specifically, compounds described in paragraphs[0023] to [0024] of JP-A-2002-62426 may be used. Aldehydes having highreactivity are preferable, and glutaraldehydes are particularlypreferable.

The amount of the added crosslinking agent is in the range of preferably0.1 to 20% by mass, and more preferably 0.5 to 15% by mass based on thepolymer. The amount of unreacted crosslinking agent remaining in thealignment film is preferably 1.0% by mass or less, and more preferably0.5 mass % or less. The adjustment as described above makes it possibleto give a sufficient endurance to the aligned film without generatingany reticulation even if the aligned film is used in a liquid crystaldisplay device for a long time or is allowed to stand still inhigh-temperature and high-humidity atmosphere for a long time.

For example, the aligned film may be formed by applying the solution onthe cellulose acylate film, drying (crosslinking) the solution byheating, and rubbing the resulting film. The cross-linking reaction, asmentioned above, may be carried out in at a predetermined stage afterthe solution is applied on the cellulose acylate film. In the case ofusing a water-soluble polymer, such as polyvinyl alcohol, as the alignedfilm forming material, a mixture solvent of water with an organicsolvent having a defoaming ability (for example, methanol) is preferablyused as the coating solution. The mass ratio of water to methanol ispreferably 0:100 to 99:1, and more preferably from 0:100 to 91:9.Accordingly, the generation of foams may be prevented in order to ensuresignificantly decreased defects in the aligned film, and the surface ofthe optically anisotropic layer.

Preferable examples of an application method of the aligned film includea spin coating method, a dip coating method, a curtain coating method,an extrusion coating method, a rod coating method, or a roll coatingmethod. The rod coating method is particularly preferable. It ispreferable that the thickness of the polymer layer after the drying be0.1 to 10 μm. The drying by heating may be performed at a temperature of20 to 110° C. In order to form cross-links to a satisfactory extent, thedrying temperature is preferably 60 to 100° C., and particularlypreferably 80 to 100° C. The drying time is generally 1 minute to 36hours, and preferably 1 to 30 minutes. Further, it is preferable toadjust the pH to an optimum value for the cross-linking agent used. Inthe case of using glutaraldehyde, the pH is generally 4.5 to 5.5, andparticularly preferably 5.

The alignment film is provided on the cellulose acylate film or theundercoat layer according to the aspect of the invention. After theabove-described polymer layer is crosslinked, the surface of the layermay be subjected to rubbing treatment to form the alignment film.

In respect to the above-mentioned rubbing treatment, the treatmentmethods extensively used to align liquid crystals performed during theproduction of liquid crystal displays may be used. That is, the methodof rubbing the surface of an alignment film in a predetermined directionby means of paper, gauze, felt, rubber, or nylon or polyester fibers maybe used to obtain alignment. In general, it can be carried out byrubbing several times the polymer surface by using cloths into whichfibers having the same length and the same diameter are transplantedevenly.

In the case of when the rubbing treatment method is industriallyperformed, it may be achieved by bringing a rotating rubbing roll intocontact with a film to which the transported polarizing film isattached. However, it is preferable that the circularity,cylindricality, and fluctuation (eccentricity) of the rubbing roll allbe 30 μm or below. It is preferable that the wrap angle of a film to therubbing roll be 0.1 to 90°. However, as disclosed in JP-A-1996-160430,there is a case that the steady rubbing treatment is ensured by windinga film around the roll at an angle of 360° or more. It is preferablethat the film be transported at a speed of 1 to 100 m/min. Further, itis preferable that the rubbing angle be in the range of 0 to 60°. In thecase of when the film is applied to a liquid crystal display device, therubbing angle is preferably 40 to 50°. In particular, it is preferableto adjust the rubbing angle to 45°.

The film thickness of the thus-obtained aligned film is preferably inthe range of 0.1 to 10 μm.

(Optically Anisotropic Layer)

Next, liquid crystal molecules of an optically anisotropic layer arealigned on the aligned film. Thereafter, the aligned film polymer may bereacted with the polyfunctional monomer contained in the opticallyanisotropic layer or crosslinked by using a crosslinking agent, ifnecessary.

The liquid crystal molecules used in the optically anisotropic layer maybe rod-like liquid crystal molecules or disk-like liquid crystalmolecules. The rod-like liquid crystal molecules and the disk-likeliquid crystal molecules may each be a high molecular weight liquidcrystal or a low molecular weight liquid crystal. Furthermore, acompound about which a low molecular weight liquid crystal iscrosslinked to exhibit no liquid crystallinity may be included.

1) Rod-Like Liquid Crystal Molecule]

As to the above rod-like liquid crystal molecule, azomethines, azoxys,cyanobiphenyls, cyanophenylesters, benzoic acid esters, cyclohexanecarboxylic acid phenylesters, cyanophenylcyclohexanes, cyano-substitutedphenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes,tolans, and alkenylcyclohexylbenzonitrils, and the like may be usedpreferably.

Furthermore, a metal complex is contained in the rod-like liquid crystalmolecule. In addition, a liquid crystal polymer that contains therod-like liquid crystal molecule in the repeating unit thereof may alsobe used as the rod-like liquid crystal molecule. In other words, therod-like liquid crystal molecule may be bonded to a (liquid crystal)polymer.

Rod-like liquid crystal molecules are described in Quarterly ChemicalReview, Vol. 22, “Chemistry of Liquid Crystal” edited by the ChemicalSociety of Japan (1994), Chapters 4, 7, and 11, and “Liquid CrystalDevice Handbook” edited by Japan Society for the Promotion of Science,142nd Committee, chapter 3.

The birefringence of the rod-like liquid crystal molecules is preferably0.001 to 0.7.

The above rod-like liquid crystal molecule preferably has apolymerizable group in order to fix the alignment state thereof. Thepolymerizable group is preferably a radical polymerizable unsaturatedgroup or a cation polymerizable group. Specific examples thereof mayinclude polymerizable groups and polymerizable liquid crystal compoundsdescribed in paragraphs [0064] to [0086] of JP-A-2002-62427.

2) Disk-Like Liquid Crystal Molecule

Examples of the disk-like (discotic) liquid crystal molecule may includebenzene derivatives disclosed in a study report of C. Destrade, Mol.Cryst., vol. 71, page 111 (1981), toluxene derivatives disclosed in astudy report of C. Destrade et al., Mol. Cryst., vol. 122, page 141(1985), and Phyics. Lett., A, vol. 78, page 82 (1990), cyclohexanederivatives disclosed in a study report of B. Kohne, Angew. Chem. Soc.,vol. 96, page 70 (1984), and macrocycles of azacrowns andphenylacetylenes disclosed in a study report of J. M. Lehn, J. Chem.Commun., page 1794 (1985), a study report of and J. Zhang et al., and J.Am. Chem. Soc. vol. 116, page 2655 (1994).

The above disk-like liquid crystal molecule may include compounds, whichshows liquid crystallization, having a structure in which straight chaingroups such as alkyl, alkoxy, and substituted benzoyloxy are radiallysubstituted as side chains of a parent core located at the center of themolecule. The above molecule or a cluster of the molecules is preferablythe compound which has rotational symmetry and may provide predeterminedalignment. As to the optically anisotropic layer produced from thedisk-like liquid crystal molecules, it is unnecessary that the compoundwhich is finally contained in the optically anisotropic layer contains adisk-like liquid crystal molecule. For example, a low molecular weightdisk-like liquid crystal molecule having a thermo- or photo-reactivegroup is polymerized or crosslinked by heat or light to form a compoundthat does not behave as liquid crystal due to the polymerization.Preferable examples of the disk-like liquid crystal molecule aredescribed in JP-A-1996-50206. Further, JP-A-1996-27284 disclosespolymerization of a disk-like liquid crystal molecule.

In order to fix the above disk-like liquid crystal molecule by using thepolymerization, it is necessary to bond a polymerizable group as asubstituent to the disk-like core of the disk-like liquid crystalmolecule. A compound where the disk-like core and the polymerizablegroup are bonded through a linking group is preferable. Accordingly, thealignment state of the compound may be kept in the polymerizationreaction. Examples of the compound may include compounds described inparagraphs [0151] to [0168] of JP-A-2000-155216.

In hybrid alignment, an angle between major axis (disc plane) ofdisk-like liquid crystal molecule and plane of polarizing film increasesor decreases with increase of distance from plane of polarizing film andin the direction of depth of the optically anisotropic layer. The aboveangle preferably decreases with increase of the distance. Further,examples of variation of the angle may include continuous increase,continuous decrease, intermittent increase, intermittent decrease,variation containing continuous increase and decrease, and intermittentvariation containing increase or decrease. The intermittent variationcontains an area where the inclined angle does not vary in the course ofthe thickness direction of the layer. The angle may totally increases ordecreases in the layer, even if it does not vary in the course. It ispreferable that the angle continuously vary.

An average direction of a major axis of a disk-like liquid crystalmolecule on the polarizing film side may be generally controlled byselecting the disk-like liquid crystal molecule or materials of thealignment layer, or by selecting methods for the rubbing treatment. Thedirection of the major axis (disc plane) of disk-like liquid crystalmolecule on the surface side (air side) may be generally controlled byselecting the disk-like liquid crystal molecule or the type of additivesused together with the disk-like liquid crystal molecule. Examples ofthe additives which are used with disk-like liquid crystal molecule mayinclude plasticizers, surfactants, and synthetic monomers and polymers.Further, the extent of variation of the alignment direction of the majoraxis may be controlled by the selection of the liquid crystal moleculesand the additives.

(Other Compositions of the Optically Anisotropic Layer)

The use of a plasticizer, a surfactant, and a polymerizable monomertogether with the above liquid crystal molecules makes it possible toimprove the uniformity of the coating film, the strength of the film,the alignment of the liquid crystal molecules, and the like. It ispreferable that these are compatible with the liquid crystal moleculesand change the inclined angle of the liquid crystal molecules or do nothinder the alignment.

The polymerizable monomer may be a radical polymerizable compound or acation polymerizable compound. It is preferably a polyfunctional radicalpolymerizable monomer. Preferably, the polymerizable monomer is amonomer copolymerizable with the above-mentioned liquid crystal compoundhaving the polymerizable group. Examples thereof may include monomersdescribed in paragraphs [0018] to [0020] of JP-A-2002-296423. Theaddition amount of the compound is in the range of generally 1 to 50% bymass and preferably 5 to 30% by mass based on the disk-like liquid

The above-mentioned surfactant may be a known compound. A fluorine-basedcompound is particularly preferable. Specific examples thereof mayinclude compounds described in paragraphs [0028] to [0056] ofJP-A-2001-330725.

Preferably, the polymer which is used together with the disk-like liquidcrystal molecules can change the inclined angle of the disk-like liquidcrystal molecules.

As an example of these polymers, cellulose acylate may be included.Preferable examples of the cellulose acylate are described in paragraph[0178] of JP-A-2000-155216. In order not to hinder the alignment of theliquid crystal molecules, the addition amount of the polymer is in therange of preferably 0.1 to 10% by mass and more preferably 0.1 to 8% bymass based on the liquid crystal molecules.

The discotic nematic liquid crystal phase-solid phase transitiontemperature of the disk-like liquid crystal molecule is in the range ofpreferably 70 to 300° C. and more preferably 70 to 170° C.

[Formation of Optically Anisotropic Layer]

The optically anisotropic layer may be formed by applying a coatingsolution, which contains the liquid crystal molecule together with thefollowing polymerization initiator or optional components, onto thealignment film.

As the solvent to be used in preparing the coating solution, it ispreferable to use an organic solvent. Examples of the organic solventinclude amides (for example, N,N-dimethylformamide), sulfoxides (forexample, dimethyl sulfoxide), heterocyclic compounds (for example,pyridine), hydrocarbons (for example, benzene and hexane), alkyl halides(for example, chloroform, dichloromethane, and tetrachloroethane),esters (for example, methyl acetate and butyl acetate), ketones (forexample, acetone, methyl ethyl ketone), and ethers (for example,tetrahydrofuran and 1,2-dimethoxyethane). Alkyl halides and ketones arepreferable. It is possible to use two or more organic solvents together.

The coating solution can be applied by using a known method (forexample, the wire bar coating method, the extrusion coating method, thedirect gravure coating method, the reverse gravure coating method, orthe die coating method).

The thickness of the optically anisotropic layer is in the range ofpreferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and particularlypreferably 1 to 10 μm.

(Fixing of the Alignment State of Liquid Crystal Molecules)

The aligned liquid crystal molecules may be fixed while the alignmentstate is maintained. The fixation is preferably carried out by using thepolymerization reaction. Examples of the polymerization reaction includea heat polymerization reaction with the use of a heat polymerizationinitiator and a photopolymerization reaction with the use of aphotopolymerization initiator. The photopolymerization reaction ispreferable.

Examples of the photopolymerization initiator include α-carbonylcompounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloinethers (described in U.S. Pat. No. 2,448,828), 1-hydrocarbon-substitutedaromatic acyloin compounds (described in U.S. Pat. No. 2,722,512),polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and2,951,758), combinations of a triarylimidazole dimer with p-aminophenylketone (described in U.S. Pat. No. 3,549,367), acridine and phenazinecompounds (described in JP-A-1985-105667 and U.S. Pat. No. 4,239,850),and oxadiazol compounds (described in U.S. Pat. No. 4,212,970).

It is preferable to use the photopolymerization initiator in an amountof 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on thesolid matters in the coating solution.

In the light radiation for polymerizing the liquid crystal molecule, itis preferable to use ultraviolet rays.

The radiation energy preferably ranges from 20 to 50 mJ/cm², morepreferably ranges from 20 to 5000 mJ/cm², and particularly preferablyranges from 100 to 800 mJ/cm². In order to accelerate thephotopolymerization reaction, the light radiation may be carried outunder heating.

A protective layer may be formed on the optically anisotropic layer.

(Combination with the Polarizing Film)

It is preferable to combine this optically compensating film with apolarizing film. Specifically, a coating solution for forming opticallyanisotropic layers, as described above, is applied onto the surface of apolarizing film, thereby forming an optically anisotropic layer. As aresult, produced is a thin polarizing plate having only small stress(strain×sectional area×elastic modulus) with a change in the size of thepolarizing film without using any polymer film between the polarizingfilm and the optically anisotropic layer. By providing a polarizingplate using the cellulose acylate film according to the aspect of theinvention into a large-sized liquid crystal display device, imageshaving a high display quality may be obtained without causing problems,such as light leakage.

The inclined angle between the polarizing film and the opticallycompensating layer is preferably adjusted by stretching the layers insuch a manner that the angle is matched with the angle between thetransmission axes of two polarizing films adhered onto both surfaces ofa liquid crystal cell which constitutes a LCD and the lengthwise orlateral direction of the liquid crystal cell. The angle is generally45°. However, in recent years, a device has been developed, in which theangle is not always 45° in respect to the latest transmission,reflection, and semi-transmission type LCDs. Therefore, it is preferablethat the stretching direction be optionally adjustable in order toconform to the design of LCD.

[Provision of an Antireflection Layer (Production of an AntireflectionFilm)]

An antireflection film is generally formed by laying a low refractiveindex layer, which functions as an antifouling property layer, and atleast one layer having a refractive index higher than that of the lowrefractive index layer (i.e., a high refractive index layer and a middlerefractive index layer), on a cellulose acylate film according to theaspect of the invention.

Examples of the method of forming a multilayered film where transparentthin films made of inorganic compounds (such as metal oxides) havingdifferent refractive indexes are laminated include a chemical vapordeposition (CVD) method, a physical vapor deposition (PVD) method, and amethod of forming a metal compound such as metal alkoxide into a filmmade of colloidal metal oxide particles by a sol-gel method, andsubjecting the film to post-treatment (ultraviolet radiation:JP-A-1997-157855, or plasma treatment: JP-A-2002-327310) to form a thinfilm.

Meanwhile, as antireflection films having a high productivity, suggestedare various antireflection films obtained by laminating thin films, eachof which is made of inorganic particles dispersed in a matrix, bycoating. Further, as the antireflection film, an antireflection film,which may be an antireflection film produced by making fineirregularities in the topmost surface of the antireflection film formedby coating to give anti-glare property to the surface, may be provided.

The cellulose acylate film according to the aspect of the invention maybe applied to an antireflection film produced by using any one of theabove-mentioned methods, but it is particularly preferable to apply thecellulose acylate film to the antireflection film produced by coatingmethod (coating type).

[Layer Structure of the Coating Type Antireflection Film]

According to the aspect of the invention, an antireflection film atleast having a layer structure obtained by sequentially forming, on acellulose acylate film, a middle refractive index layer, a highrefractive index layer, and a low refractive index layer (the outermostlayer), is designed to have refractive indexes satisfying the followingrelationship:

the refractive index of the high refractive index layer>the refractiveindex of the middle refractive index layer>the refractive index of thecellulose acylate film>the refractive index of the low refractive indexlayer.

A hard coating layer may be formed between the cellulose acylate filmand the middle refractive index layer. Further, the antireflection filmmay be composed of a middle refractive index hard coating layer, a highrefractive index layer, and a low refractive index layer. With regardthe above antireflection film, examples thereof are described inJP-A-1996-122504, JP-A-1996-110401, JP-A-1998-300902, JP-A-2002-243906,and JP-A-2000-111706.

Different functions may be provided to the layers. Examples of thelayers may include a low refractive index layer having antifoulingproperty and a high refractive index layer having antistatic property(for example, JP-A-1998-206603, JP-A-2002-243906, and the like).

The haze of the antireflection film is preferably 5% or less and morepreferably 3% or less. The strength of the film is preferably H or more,more preferably 2H or more, and particularly preferably 3H or harder, interms of the pensile hardness test, according to JIS K5400.

(High Refractive Index Layer and Middle Refractive Index Layer)

The higher refractive index layer of the antireflection film is formedof a curable film containing at least inorganic compound superfineparticles having a high refractive index and an average particle size of100 nm or less, and matrix binder.

The inorganic compound fine particles having the high refractive indexmay be made of an inorganic compound having a refractive index of 1.65or more and preferably a refractive index of 1.9 or more. Examples ofthe inorganic compound fine particles having the high refractive indexmay include oxides of Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, In, and the like,and composite oxides containing these metal atoms.

In order to ensure the superfine particles, a process in which theparticles whose surface is treated with a surface-treating agent (forexample, a process of performing treatment by using a silane couplingagent disclosed in JP-A-1999-295503, JP-A-1999-153703, andJP-A-2000-9908, or a process of performing treatment by using an anioniccompound or an organometallic coupling agent disclosed inJP-A-2001-310432 and the like), a process in which a core-shellstructure is formed to have high refractive index particles as a core(for example, a process disclosed in JP-A-2001-166104), and a processusing a specific dispersing agent (for example, a process disclosed inJP-A-1999-153703, U.S. Pat. No. 6,210,858B1, JP-A-2002-2776069, and thelike) may be used. The material which forms the matrix binder may be anyone of known thermoplastic resins and thermosetting resins film.

Further, the material which forms the matrix binder is preferably atleast one composition selected from a composition including apolyfunctional compound containing at least two radical polymerizablegroups and/or cation polymerizable groups, a composition including anorganometallic compound containing a hydrolyzable group, and acomposition including a partial condensate thereof. The compounds usedin the composition may be compounds that are described inJP-A-2000-47004, JP-A-2001-315242, JP-A-2001-31871, JP-A-2001-296401,and the like.

Further, a curable film obtained from a colloidal metal oxide and ametal alkoxide composition formed from a hydrolysis condensate of ametal alkoxide is preferably used. Examples thereof may include curablefilms that are described in JP-A-2001-293818 and the like.

The refractive index of the high refractive index layer is generally inthe range of 1.70 to 2.20. The thickness of the high refractive indexlayer is in the range of preferably 5 nm to 10 μm and more preferably 10nm to 1 μm.

The refractive index of the middle refractive index layer is adjusted soas to become a value between the refractive index of the low refractiveindex layer and the refractive index of the high refractive index layer.The refractive index of the middle refractive index layer is preferablyin the range of 1.50 to 1.70.

[Low Refractive Index Layer]

The low refractive index layer is laminated on the high refractive indexlayer. The low refractive index layer has a refractive index generallyin the range of 1.20 to 1.55 and preferably in the range of 1.30 to1.50.

The above low refractive index layer is preferably formed as anoutermost layer having scratch resistance and antifouling property. Inorder to significantly improve the scratch resistance, it is effectiveto give lubricity to the surface. Specifically, it is possible to usethe method of forming the thin film layer by using known siliconecompounds or fluorine-containing compounds.

The refractive index of the fluorine-containing compound is preferably1.35 to 1.50 and more preferably 1.36 to 1.47. The preferablefluorine-containing compound is the compound that contains 35 to 80% bymass of fluorine atoms and has crosslinkable or polymerizable functionalgroups.

As the above fluorine-containing compounds, compounds that are describedin paragraphs [0018] to [0026] of JP-A-1997-222503, paragraphs [0019] to[0030] of JP-A-1999-38202, paragraphs [0027] to [0028] ofJP-A-2001-40284, JP-A-2000-284102, and the like may be used.

Preferably, the above silicone compound is a compound which has apolysiloxane structure, and a compound which contains, in the polymerchain thereof, a curable functional group or polymerizable functionalgroup so as to have a crosslinked structure in the film to be formed.Examples thereof may include reactive silicones (for example, Silaplanemanufactured by Chisso Corporation), and polysiloxane containing at bothends thereof silanol groups (JP-A-1999-258403), and the like.

It is preferable to conduct the crosslinking or polymerizing reaction ofthe fluorine-containing polymer and/or the siloxane polymer having acrosslinkable or polymerizable group, by radiation of light or heatingat the same time of or after applying a coating composition for formingan outermost layer containing a polymerization initiator, a sensitizer,and the like.

Further, preferable is a sol-gel cured film obtained by curing anorganometallic compound, such as a silane coupling agent, and a silanecoupling agent which contains a specific fluorine-containing hydrocarbongroup, in the presence of a catalyst, by condensation reaction.

Examples thereof may include silane compounds which contain apolyfluoroalkyl group, or partially-hydrolyzed condensates (compoundsdisclosed in JP-A-1983-142958, JP-A-1983-147483, JP-A-1983-147484,JP-A-1997-157582, and JP-A-1999-106704), silyl compounds which containsa poly(perfluoroalkyl ether) group, which is a long chain groupcontaining fluorine (compounds described in JP-A-2000-117902,JP-A-2001-48590, and JP-A-2002-53804), and the like.

It is preferable that the low refractive index layer be made to contain,as an additive other than the above, a filler (for example, silicondioxide (silica), low refractive index inorganic compound particleshaving a primary average particle size of 1 to 150 nm made, for example,of fluorine-containing particles (magnesium fluoride, calcium fluoride,barium fluoride, and the like), organic fine particles, as described inparagraphs [0020] to [0038] of JP-A-1999-3820), a silane coupling agent,a lubricant, a surfactant, and the like.

In the case of when the low refractive index layer is positioned beneaththe outermost layer, the low refractive index layer may be formed byusing a gas phase method (a vacuum vapor deposition, a sputteringmethod, an ion plating method, a plasma CVD method, or the like). Thelow refractive index layer is preferably formed by using a coatingmethod because the layer can be formed at low costs.

The thickness of the low refractive index layer is preferably 30 to 200nm, more preferably 50 to 150 nm, and particularly preferably 60 to 120nm.

(Hard Coating Layer)

The hard coating layer may be formed on the surface of the celluloseacylate film to provide a sufficient mechanical strength to anantireflection film. Particularly, the hard coating layer is preferablydisposed between the cellulose acylate film and the above highrefractive index layer.

The hard coating layer is preferably formed by crosslinking reaction orpolymerizing reaction of a curable compound through light and/or heat.The curable functional group is preferably a photopolymerizablefunctional group, and an organometallic compound which contains ahydrolyzable functional group is preferably an organic alkoxysilylcompound.

Specific examples of these compounds are the same as those of the highrefractive index layer.

Specific examples of the composition which constitutes the hard coatinglayer may include matters described in JP-A-2002-144913, JP-A-2000-9908,and WO 0/46617.

The above high refractive index layer may act as a hard coating layer.In this case, it is preferable to use the manner described about on thehigh refractive index layer, to disperse particles finely to beincorporated into the hard coating layer to be formed.

The hard coating layer may contain particles having an average particlesize of 0.2 to 10 μm, so as to be caused to function as an anti-glarelayer. The anti-glare layer has an anti-glare function, which will bedetailed in the below.

The film thickness of the hard coating layer may be appropriately setaccording to the purpose thereof. The film thickness of the hard coatinglayer is preferably 0.2 to 10 μm and more preferably 0.5 to 7 μm.

The strength of the hard coating layer is preferably H or harder, morepreferably 2H or harder, and particularly preferably 3H or harder, interms of the pensile hardness, according to a JIS K5400 test. The hardcoating layer is preferably one which is less in an abrasion amount ofthe sample in a taber test according to JIS K5400.

(Forward Scattering Layer)

In the case of when a forward scattering layer is applied to a liquidcrystal display device, the forward scattering layer may be provided inorder to improve the viewing angle of the display device when the angleof visibility is inclined up and down or right and left. Both of a hardcoat function and a forward scattering function may be ensured bydispersing fine particles having different refractive indexes in theabove hard coating layer.

For example, processes may be used, which are described inJP-A-1999-38208 in which the forward scattering coefficient isspecified, in JP-A-2000-199809 in which the relative refractive indexesof a transparent resin and fine-particles are set to fall in thespecific ranges, and in JP-A-2002-107512 in which the haze value is setto 40% or more.

(Other Layers)

In addition to the above-mentioned layers, a primer layer, ananti-static layer, an undercoating layer, or a protective layer may befurther formed.

(Coating Methods)

The layers of the antireflection film may be formed by performingcoating using a dip coating method, an air knife coating method, acurtain coating method, a roller coating method, a wire bar coatingmethod, a gravure coating method, a micro gravure method, or anextrusion coating method (specification of U.S. Pat. No. 2,681,294).

(Antiglare Function)

The anti-reflection film may have an antiglare function scattering lightfrom the outside. The antiglare function may be obtained by makingunevenness in a surface of the anti-reflection film. In the case of whenthe anti-reflection film has the antiglare function, the haze of theanti-reflection film is preferably 3 to 30%, more preferably 5 to 20%,and most preferably 7 to 20%.

In order to form prominences and depressions on the surface of theantireflection film, any method may be used as long as the method iscapable of desirably maintaining the shape of surface. Examples of themethod may include a method of using fine particles in the lowrefractive index layer to form prominences and depressions on thesurface of the film (for example, JP-A-2000-271878, and the like), amethod of adding a small amount (0.1 to 50% by mass) of relatively largeparticles (particle size: 0.05 to 2 μm) to the layer (high refractiveindex layer, middle refractive index layer, or hard coating layer) to beformed beneath the low refractive index layer so as to form a filmhaving an uneven surface, and then forming the low refractive indexlayer thereon while keeping this uneven surface form to provide the lowrefractive index layer (for example, JP-A-2000-281410, JP-A-2000-95893,JP-A-2001-100004, JP-A-2001-281407, and the like), and a method ofphysically transferring prominences and depressions onto the surface ofa topmost layer (antifouling layer) formed by coating (for example,JP-A-1988-278839, JP-A-1999-183710, and JP-A-2000-275401 as an embossingmethod).

<Liquid Crystal Display Device>

The cellulose acylate film according to the aspect of the invention, andthe polarizing plate, the retardation film, and the optical film usingthe cellulose acylate film may be desirably provided in a liquid crystaldisplay. Hereinafter, liquid crystal modes will be described.

(TN Mode Liquid Crystal Display Device)

The liquid crystal display device of TN mode is most frequently used asa color TFT liquid crystal display device, and hence is described inmany documents. The alignment state of the liquid crystal cell in the TNmode at the time of black display is the state that rod-like liquidcrystal molecules stand up in the central portion of the cell and therod-like liquid crystal molecules lie down in portions near substratesof the cells.

(OCB Mode Liquid Crystal Display Device)

The liquid crystal display device of OCB mode is a liquid crystal cellof bend alignment mode in which rod-like liquid crystal molecules inupper part and ones in lower part are substantially reversely(symmetrically) aligned. A liquid crystal display device having theliquid crystal cell of bend alignment mode is disclosed in U.S. Pat.Nos. 4,583,825 and 5,410,422. Since rod-like liquid crystal molecules inupper part and lower part of the liquid crystal cell are symmetricallyaligned, the liquid crystal cell of bend alignment mode has self-opticalcompensatory function. Therefore, this liquid crystal mode is referredto as OCB (optically compensated bend) liquid crystal mode.

In the same manner as in the TN mode, in a liquid crystal cell in theOCB mode, the alignment state of the liquid crystal cell at the time ofblack display is the state that rod-like liquid crystal molecules standup in the central portion of the cell and the rod-like liquid crystalmolecules lie down in portions near substrates of the cells.

EXAMPLES

Hereinafter, the invention will be described in more detail withreference to Examples and Comparative examples. Materials, the amount,the ratio, treatment processes, and the order of treatment which aredisclosed in the following Examples may be appropriately changed withoutdeviation from the scope of the invention. However, the scope of theinvention is not limited to the following specific examples.

(Evaluation of Physical Properties)

(1) Weight Average Molecular Weight

Measurement was performed by using a GPC device (HLC-8220GPCmanufactured by TOSOH CORPORATION) under the following condition toobtain a weight average molecular weight (Mw). In addition, acalibration curve was obtained by using polystyrene (TSK standardpolyslen: molecular weight 1050, 5970, 18100, 37900, 190000, and706000). The obtained average molecular weight was divided by amolecular weight per one repeating unit that was obtained by using thesubstitution degree determined by the following method (2) to ensure thedegree of weight average polymerization (DPw).

Eluting solution: dimethylformamide (DMF)

Flow rate: 1 ml/min

Detector: RI

Concentration of the sample: 0.5%

(2) Substitution Degree

Area strength ratios of carbon atoms of the cellulose acylate werecompared to each other by using a ¹³C-NMR method to determine thesubstitution degree.

(3) Glass Transition Temperature (Tg)

The cellulose acylate film was put onto a measurement pan of DSC in anamount of 20 mg. The film was heated in a nitrogen atmosphere from 30°C. to 240° C. at a heating rate of 10° C./min, and then cooled to 30° C.at a cooling rate of −50° C./min. Next, the temperature was increasedagain from 30° C. to 240° C., and the temperature at which the base linestarted to be displaced at low temperatures was set to Tg.

(4) Quantitative Analysis of Fine Particles

10 g of cellulose acylate was dissolved in 40 ml of dichloromethane,dried by using an applicator on a glass plate, and flow cast so as toensure a thickness of about 50 μm. The resulting structure was observedby using a polarization microscope (parallel and cross nicols), and theamount and size of impurity per unit area were obtained.

(5) Quantitative Analysis of Sulfur Components

About 0.5 g of the dried cellulose acylate sample was carbonized in anelectric furnace to measure the amount of sulfur components by using anoxidation decomposition coulometrical titration method.

(6) Quantitative Analysis of Metal

About 0.5 g of the dried cellulose acylate sample was nitrocarburized byusing a multiwave method to measure the amounts of sodium, potassium,calcium, and magnesium using ICP.

Example 1 Synthetic Example 1 Cellulose Acetate Propionate P-1, P-11

10 parts by mass of cellulose (hardwood pulp) and 5 parts by mass ofacetic acid were put into a reactor and left at 25° C. for 1 hour(pretreatment). After the reactor was cooled to 0° C., a mixture of 103parts by mass of propionic anhydride and 1.0 parts by mass of sulfuricacid was prepared, cooled to −10° C., and added to the cellulose thatwas subjected to the pretreatment in advance all at once. After 30 min,the temperature of the outside of the reactor was increased to 30° C.and the reaction was continued for 4 hours. The reactor was cooled in anice bath at 5° C. and 120 parts by mass of acetic acid containing 25% ofwater was added for 30 min. The temperature of the inside of the reactorwas increased to 60° C. and agitation was performed for 2 hours. 50%aqueous solution of magnesium acetate tetrahydrate was added in anamount of 10 parts by mass, and agitation was performed for 30 min.

75 parts by mass of acetic acid containing 25% of water and 250 parts bymass of water were slowly added to precipitate cellulose acetatepropionate. After washing was performed using hot water at 70° C. untilthe pH of the washing solution was 6 to 7, agitation was performed for0.5 hours in a 0.001% aqueous solution of calcium hydroxide to achievefiltration. The obtained cellulose acetate propionate P-1 was dried at70° C. According to ¹H-NMR and GPC measurements, the cellulose acetatepropionate thus obtained had the acetylation degree of 0.16, thepropionylation degree of 2.55, and the weight average molecular weightof 135,000. Furthermore, the melt viscosity of cellulose propionate was840 Pa·s at 230° C.

100 parts by mass of cellulose acetate propionate P-1 and 2000 parts bymass of acetic acid were mixed with each other and agitated at 40° C. toproduce a homogeneous solution. The solution was sequentially filteredby using a filtering paper made of cellulose fibers (retention particlesize of 40 μm), a sintered metal filter (retention particle size of 10μm), and a sintered metal filter (retention particle size of 10 μm)while being pressurized to remove impurities. In addition, 75 parts bymass of acetic acid containing 25% of water and 250 parts by mass ofwater were slowly added to precipitate cellulose acetate propionate.After washing was performed using hot water at 70° C. until the pH ofthe washing solution was 6 to 7, agitation was performed for 0.5 hoursin a 0.001% aqueous solution of calcium hydroxide to achieve filtration.The obtained cellulose acetate propionate was dried at 70° C. Accordingto ¹H-NMR and GPC measurements, the cellulose acetate propionate P-11thus obtained had the acetylation degree of 0.16, the propionylationdegree of 2.55, and the weight average molecular weight of 134,000.Furthermore, the melt viscosity of cellulose acylate was 830 Pa·s at230° C.

Synthetic Example 2 Cellulose Acetate Propionate P-2, P-12

150 parts by mass of cellulose (linter) and 100 parts by mass of aceticacid were put into a reactor and left at 25° C. for 1 hour(pretreatment). After the reactor was cooled to 0° C., a mixture of 1545parts by mass of propionic anhydride and 10.5 parts by mass of sulfuricacid was prepared, cooled to −15° C., and added to the cellulose thatwas subjected to the pretreatment in advance all at once. After 30 min,the temperature of the outside of the reactor was slowly increased andcontrolled to be 30° C. 2 hours after an acylation agent was added. Thereactor was cooled in an ice bath at 5° C. and controlled so as to havethe inside temperature of 10° C. 5 hours after the acylation agent wasadded. 120 parts by mass of acetic acid containing 25% water that wascooled to 5° C. was added for 1 hour. The inside temperature wasincreased to 60° C. and agitation was performed for 2 hours. A solutionin which magnesium acetate tetrahydrate was dissolved in an amount twotimes as high as a mole concentration of sulfuric acid was added to anacetic acid containing 50% water, and agitation was performed for 30min.

1000 parts by mass of acetic acid containing 25% of water, 500 parts bymass of acetic acid containing 33% of water, 500 parts by mass of aceticacid containing 50% of water, and 1000 parts by mass of water weresequentially added to precipitate cellulose acetate propionate. Afterwashing was performed using hot water at 70° C. until the pH of thewashing solution was 6 to 7, agitation was performed for 0.5 hours in a0.001 wt % aqueous solution of calcium hydroxide at 20° C. to achievefiltration. The obtained cellulose acetate propionate was dried in avacuum at 70° C. According to ¹H-NMR and GPC measurements, the celluloseacetate propionate P-2 thus obtained had the acetylation degree of 0.40,the propionylation degree of 2.45, and the weight average molecularweight of 129,000. Furthermore, the melt viscosity of cellulosepropionate was 790 Pa·s at 230° C.

In respect to the cellulose acetate propionate P-2, the dissolution andthe filtration were performed by using the same procedure as P-1 toobtain the cellulose acetate propionate P-12. According to ¹H-NMR andGPC measurements, the cellulose acetate propionate P-12 thus obtainedhad the acetylation degree of 0.40, the propionylation degree of 2.45,and the weight average molecular weight of 127,000. Furthermore, themelt viscosity of cellulose propionate was 800 Pa·s at 230° C.

Synthetic Example 3 Cellulose Acetate Butyrate B-1

10 parts by mass of cellulose (hardwood pulp) and 13.5 parts by mass ofacetic acid were put into a reactor and left at 25° C. for 1 hour. Afterthe reactor was cooled to 0° C., a mixture of 108 parts by mass ofbutyric anhydride and 1.0 parts by mass of sulfuric acid was prepared,cooled to −20° C., and added to the cellulose that was subjected to thepretreatment in advance all at once. After 1 hour, the temperature ofthe outside of the reactor was increased to 27° C. and the reaction wascontinued for 6 hours. The reactor was cooled in an ice bath at 5° C.and 120 parts by mass of acetic acid containing 25% of water was addedfor 30 min. The temperature of the inside of the reactor was increasedto 60° C. and agitation was performed for 2.5 hours. 50% aqueoussolution of magnesium acetate tetrahydrate was added in an amount of 10parts by mass, and agitation was performed for 30 min.

75 parts by mass of acetic acid containing 25% of water and 250 parts bymass of water were slowly added to precipitate cellulose acetatebutyrate. After washing was performed using hot water at 70° C. untilthe pH of the washing solution was 6 to 7, agitation was performed for0.5 hours in a 0.002% aqueous solution of calcium hydroxide to achievefiltration. The obtained cellulose acetate butyrate B-1 was dried at 70°C. According to ¹H-NMR and GPC measurements, the cellulose acetatebutyrate B-1 thus obtained had the acetylation degree of 0.80, thebutyrylation degree of 1.95, and the weight average molecular weight of127,000. Furthermore, the melt viscosity of cellulose propionate was 720Pa·s at 230° C.

In respect to the cellulose acetate butyrate B-1, the dissolution andthe filtration were performed by using the same procedure as P-1 toobtain the cellulose acetate butyrate B-11.

The cellulose acetate butyrate B-11 thus obtained had the acetylationdegree of 0.80, the butyrylation degree of 1.95, and the weight averagemolecular weight of 127,000. Furthermore, the melt viscosity ofcellulose butyrate was 710 Pa·s at 230° C.

Synthetic Example 4

The procedure of Synthesis Example 1 was repeated to produce celluloseacetate propionate P-21, except that Celite 545 (goods manufactured byCelite Corporation and particle size was 20 to 80 μm) was added in anamount of 10% by mass based on the weight of solution immediately beforethe filtration and agitation and dispersion were then performed. Theobtained cellulose acetate propionate P21 had the acetylation degree of0.16, the propionylation degree of 2.55, and the weight averagemolecular weight of 132,000. Furthermore, the melt viscosity ofcellulose acylate was 830 Pa·s at 230° C.

Synthetic Example 5 Synthesis of Cellulose Acetate Propionate P-3

0.1 parts by mass of acetic acid and 2.7 parts by mass of propionic acidwere sprayed on 10 parts by mass of cellulose (hardwood pulp), andstored at room temperature for 1 hour. Separately, a mixture of 1.2parts by mass of acetic anhydride, 61 parts by mass of propionicanhydride, and 0.7 parts by mass of sulfuric acid was prepared, cooledto −10° C., and mixed with the cellulose that was subjected to thepretreatment in advance in a reactor. After 30 min, the temperature ofthe outside of the reactor was increased to 30° C. and the reaction wascontinued for 4 hours.

About 10 g of solution was sampled from the reaction solution, added tothe acetic acid aqueous solution to perform reprecipitation, washed withhot water, and dried, and an average molecular weight thereof wasobtained by using the GPC method. In connection with this, a numberaverage molecular weight was 55400 and a weight average molecular weightwas 138,400.

A reaction finishing agent that was produced by cooling 46 parts by massof acetic acid containing 25% water to −5° C. was added while a reactiondevice was cooled so as to prevent the temperature of the reactionmixture from being 23° C. or more. In this connection, the required timewas 20 min. The reaction solution was sampled and the average molecularweight was measured by using the same procedure as the case of beforethe reaction was finished. In connection with this, a number averagemolecular weight was 55,300 and a weight average molecular weight was137,900.

The inside temperature was increased to 60° C. and agitation wasperformed for 2 hours. A solution in which magnesium acetatetetrahydrate, an acetic acid, and water were mixed with each other inthe same amount was added in an amount of 6.2 parts by mass, andagitation was performed for 30 min. The reaction solution wassequentially filtered by using sintered metal filters having retentionparticle sizes of 40 μm, 10 μm, and 5 μm while being pressurized toremove impurities. The reaction solution after the filtration was mixedwith an acetic acid containing 75% of water to precipitate celluloseacetate propionate, and washing was performed using hot water at 70° C.until the pH of the washing solution was 6 to 7. In addition, agitationwas performed for 0.5 hours in a 0.001% aqueous solution of calciumhydroxide, and filtration was then conducted. The obtained celluloseacetate propionate was dried at 70° C. According to ¹H-NMR measurements,the cellulose acetate propionate P-3 thus obtained had the acetylationdegree of 0.15, the propionylation degree of 2.62, total acylsubstitution degree of 2.77, the number average molecular weight of54500 (number average polymerization degree DPn=173), the weight averagemolecular weight of 132000 (weight average polymerization degreeDPw=419), the remaining sulfuric acid content of 45 ppm, the magnesiumcontent of 8 ppm, the calcium content of 46 ppm, the sodium content of 1ppm, the potassium content of 1 ppm, and the iron content of 2 ppm.Furthermore, the melt viscosity of cellulose acetate propionate was 780Pa·s at 230° C.

In respect to the cellulose acetate propionate P-3, the dissolution andthe filtration were performed by using the same procedure as P-1 toobtain the cellulose acetate propionate P-13. According to ¹H-NMR andGPC measurements, the cellulose acetate propionate P-13 thus obtainedhad the acetylation degree of 0.15, the propionylation degree of 2.61,and the weight average molecular weight of 133,000. Furthermore, themelt viscosity of cellulose propionate was 780 Pa·s at 230° C.

Example 2 Production 1 of a Melt Cast Film

(1) Preparation of a Sample

0.3% by mass of sumilizer GP (goods manufactured by Sumitomo ChemicalCo., Ltd.) as a thermal stabilizer and 1% by mass of ADK STAB LA-31(goods manufactured by ADEKA CORPORATION) as a ultraviolet absorbingagent were added to cellulose acylate produced in Example 1, the matterof Comparative Example (see Table 1), and CTA-1 (cellulose acetate:acetyl substitution degree of 2.85) that was not within the scope of theinvention, and desirably agitated.

(2) Melt Casting

The cellulose acylate was shaped into cylindrical pellets having adiameter of 3 mm and a length of 5 mm and then dried in a vacuum drierat 110° C. for 6 hours so that residual moisture content was 0.01% bymass or less. The pellets were added into a hopper, a temperature ofwhich was controlled to Tm−10° C., and kneading melting was performed ina nitrogen atmosphere at a melting temperature of 230° C. by using afull flight screw having a compression ratio of 3.5 so that a ratio of L(the length of the screw)/D (the diameter of the screw) was 30. Inaddition, after the breaker plate type of filtration was performed at anoutlet of an extruder, the resulting structures passed through a gearpump and a lip disk filter that was made of stainless steel and had thesize of 4 μm.

CTA-1 that was not within the scope of the invention could not shapedinto pellets under the above-mentioned condition.

The pellets other than CTA-1 were extruded through a T die and cast byusing the touch roll that was disclosed in Example 1 ofJP-A-1999-235747. The resulting structure was peeled off from thecasting roll and wound. Both edges of the structure (each sidecorresponded to 3% of the total width) were trimmed immediately beforethe winding, knurlings each having a width of 10 mm and a height of 50μm were attached to the both edges thereof, and the winding wasperformed to ensure the roll shape. The amount of remaining organicsolvent of each of the films (gas chromatography method) was 0.01% bymass or less.

The surface state of each of the films was observed with the naked eye,and the level at which the movable line was not observed was evaluatedto be acceptable. In addition, permeability of light was measured inviews of 100 μm conversion.

Additionally, the number of impurities having the particle size of 40 μmor more was converted into a value per 1 g of film.

TABLE 1 Cellulose Re Rth Permeability Amount of Sample acylate (nm) (nm)Surface state (%) impurity Note 101 P-1 2 1 Nonuniform line 90 14Comparative example 102 P-2 1 2 Nonuniform line 90 11 Comparativeexample 103 B-1 0 1 Nonuniform line 90 23 Comparative example 104 CTA-1— — — — — Comparative example 105 P-11 1 1 Acceptable 92 0.01 Presentinvention 106 P-12 0 1 Acceptable 92 0.005 Present invention 107 P-21 01 Acceptable 92 0.003 Present invention 108 B-11 −1   1 Acceptable 920.005 Present invention

It was confirmed that the film which was produced by using the celluloseacylate according to the aspect of the invention had the very smallamount of impurity and acceptable physical properties. P-21 that wasproduced by using the filtration had the particularly small amount ofimpurity. Meanwhile, the samples of Comparative Examples P-1, P-2, P-3,and B-1 had the very large amount of impurity and the poor surfacestate. Thus, it is difficult to commercialize the samples of ComparativeExamples as optical films.

(Production and Evaluation of the Stretched Film)

The produced cellulose acylate films (unstretched cellulose acylatefilms) were subjected to 15% TD stretching at the temperature that was10° C. higher than Tg of the cellulose acylate film (stretched celluloseacylate film). The cellulose acylate film that was produced by using theproduction method according to the aspect of the invention hadacceptable transparency even when the cellulose acylate film wasstretched.

TABLE 2 Cellulose Re Rth Sample acylate (nm) (nm) Surface statePermeability (%) Note 201 P-1 40 63 Nonuniform line 90 Comparativeexample 202 P-2 45 70 Nonuniform line 90 Comparative example 203 B-1 5076 Nonuniform line 90 Comparative example 204 P-3 35 55 Nonuniform line90 Comparative example 205 P-11 42 68 Acceptable 92 Present invention206 P-12 46 73 Acceptable 92 Present invention 207 P-21 41 68 Acceptable92 Present invention 208 B-11 49 78 Acceptable 92 Present invention 209P-13 35 53 Acceptable 92 Present invention

Example 3 Production of the Melt Cast Film

(Production of the Cellulose Acylate Solution)

(i) Preparation of the Solvent

The solvent that contained compositions of dichloromethane (82.0% bymass), methanol (15.0% by mass), and butanol (3.0% by mass) wasprepared.

(ii) Drying of the Cellulose Acylate Composition

The cellulose acylate composition was dried so that the water contentwas 0.5% or less.

(iii) Addition of Additives

Additives of the following compositions were added to the solventobtained in step i. Furthermore, the following addition amounts (mass %)are all ratios with respect to the steady dry weight of the celluloseacylates.

[Composition of additives] Plasticizer A (triphenyl phosphate) 3.1% bymass Plasticizer B (biphenyldiphenyl phosphate)   1% by mass Opticallyanisotropy controlling agent (plate-shaped 2.95% by mass  compounddescribed in (Chemical Formula 1) of JP-A-2003-66230 UV agent a(2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di- 0.5% by masstert-butylanilino)-1,3,5-triazine) UV agent b(2(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5- 0.2% by masschlorobenzotriazole UV agent c(2(2′-hydroxy-3′,5′-di-tert-amylphenyl)-5- 0.1% by masschlorobenzotriazole) Citric acid ethyl ester (monoester:diester = 1:1)0.2% by mass(iv) Swelling-Dissolution

The cellulose acylate of step ii was added with agitation to thesolution containing the additives obtained in step iii. After stoppingthe agitation, the cellulose acylate was subjected to swelling at 25° C.for 3 hours to produce slurry. The slurry was stirred again tocompletely dissolve the cellulose acylate.

(v) Filtration-Concentration

Next, the slurry was filtered through a filter paper having an absolutefiltration precision of 0.01 mm (Toyo Roshi Co., Ltd., #63) andadditionally filtered through a filter paper having an absolutefiltration precision of 2.5 μm (Pall, Ltd., FH025) to obtain a celluloseacylate solution. The concentration of the cellulose acylate solutionwas 25% by mass (total solids content×100/(total solids content+amountof solvent)).

(Solution Casting)

The cellulose acylate solution described above was warmed up to 35° C.and flow cast on a mirror-surfaced stainless steel support by thefollowing band method. According to the band method, the celluloseacylate solution was flow cast through a delivery valve on amirror-surfaced stainless steel support with a band of 60 m in lengthand maintained at 15° C. The delivery valve used was one similar to thetype described in JP-A-1999-314233. Additionally, the temperature in thechamber of the flow casting part was set at 40° C., and the air for heatsupply was blown at a rate of 30 m/sec. At the point when the remainingsolvent reaches 100% by mass, the cellulose acylate film was peeled offfrom the mirror-surfaced stainless steel support at a load of 20 g/cm,and the temperature was elevated (temperature elevation or lowering)between 40° C. and 120° C. such that the rate of temperature elevationwas 30° C./min. Subsequently, the cellulose acylate film was dried at120° C. for 5 minutes and at 145° C. for 20 minutes, and then slowlycooled at a rate of 30° C./min to obtain a cellulose acylate film. Theobtained film was trimmed by 3 cm at both edges, provided with knurlingof 100 μm in height at positions 2 to 10 mm away from both edges, andtaken up by winding on a roll.

Re, Rth, the surface state, and the light permeability of the celluloseacylate film produced by the above-mentioned method were evaluated.

Like the melt casting method, the cellulose acylate film that wasproduced by using the solution casting method had the small amount ofimpurity and acceptable physical properties.

Additionally, in respect to the cellulose acylate film that was producedby using the solution casting method, the stretched film was produced byusing the same procedure as the cellulose acylate film that was producedby the melt casting method. Accordingly, the cellulose acylate film thatwas produced by using the production method according to the aspect ofthe invention had acceptable transparency.

Example 4 Production 2 of the Melt Cast Film

(1) Preparation of Cellulose Acylate

The samples that were disclosed in Examples 1 to 5 and ComparativeExamples 1 to 3 were used.

(2) Pelletization of Cellulose Acylate

80 parts by weight of the above-mentioned cellulose acylate, 20 parts byweight of pieces that were obtained by pulverizing edges of thecellulose acylate film as described below, and 0.3 parts by weight ofstabilizer (sumilizer GP manufactured by Sumitomo Chemical Co., Ltd.)were mixed with each other. These were dried at 100° C. for 3 hours sothat the water content was 0.1 wt % or less, melted at 180° C. by usinga twin screw kneader, extruded in hot water at 60° C. to form strands,and cut to produce cylindrical pellets having a diameter of 3 mm and alength of 5 mm.

(3) Melt Casting

The pellets were dried at 100° C. for 5 hours by using adehumidification wind at a dew point of −40° C. so that the watercontent was 0.01 wt % or less, charged into a hopper of a uniscrewkneading extruder at 80° C., and melted by using a melt extruder thatwas adjusted at 180° C. (inlet temperature) to 230° C. (outlettemperature). In addition, the diameter of the used screw was 60 mm, L/Dwas 50, and a compression ratio was 4. The resin that was extruded fromthe melt extruder was transported after the amount thereof was gauged byusing a gear pump. In connection with this, the number of rotation ofthe extruder was changed so that the resin pressure before the gear pumpwas controlled to 10 MPa. The melt resin that was transported from thegear pump was filtered by using the lip disk filter having filtrationprecision of 5 μmm, and the melt (the melt of cellulose acylate) wasextruded from a hanger coat die having a slit interval of 0.8 mm at 230°C. through a static mixer to a casting drum (CD). The melt was extrudedon three continuous cast rolls at Tg (the glass transitiontemperature)−5° C., Tg, and Tg−10° C., and a touch roll came intocontact with the cast roll of the uppermost stream so that the appliedpressure was 1.5 MPa. In addition, the temperature of the touch roll wascontrolled to Tg−5° C. by using the device that was disclosed in Example1 of JP-A-1999-235747 (double suppression roll) (the outer thickness ofthe thick metal cylinder was set to 3 mm). The term “applied pressure”means a value that is obtained by dividing a load applied to the touchroll by a contact area of the touch roll and the casting roll.

The solidified melt was peeled off from the casting drum, and both edgesthereof (5% of the total width) were trimmed immediately before thewinding. The trimmed melt was cut to sizes of 0.5 cm², and dissolvedagain during the pelletization to be used as the raw material of thefilm.

After the trimming, knurlings each having a width of 10 mm and a heightof 50 μm are attached to both edges of the cast film to obtain anunstretched film having a width of 1.5 m and a length of 3000 m at 30m/minute. Tg was measured by using DSC through the following method, andthe results are described in Table 1.

(Measurement of Tg) 20 mg of the sample was put into a measurement panof DSC. The sample was heated in a nitrogen atmosphere from 30° C. to250° C. at 10° C./min (1st-run), and then cooled to 30° C. at −10°C./min. Next, the temperature was increased from 30° C. to 250° C.(2nd-run). During the 2nd-run, the temperature at which the base linestarted to be leaned from the low temperature was considered as theglass transition temperature (Tg).

In addition, the amount of remaining solvent of the film was measure byusing the above-mentioned method. As a result, the remaining solvent wasnot measured.

(4) Evaluation of the Cast Film

Physical properties of the cellulose acylate film were measured by usingthe same method as Example 2. In this Example, the film that wasproduced by using the cellulose acylate according to the productionmethod of the aspect of the invention had the small amount of fineimpurity, the die line or the stage of the film surface that were notnonuniform, and the desirable surface state.

Example 5 Application of the Cellulose Acylate Film

(Production and Evaluation of the Stretched Film)

The cellulose acylate films (unstretched cellulose acylate films) thatwere produced in Examples 2 to 4 were subjected to 15% TD stretching atthe temperature that was 10° C. higher than Tg of each cellulose acylatefilm (stretched cellulose acylate film).

(Production and Evaluation of a Polarizing Plate)

(1) Saponification of the Cellulose Acylate Film

The unstretched cellulose acylate film and the stretched celluloseacylate film were subjected to the saponification by using the followingmethod.

A 1.5 mol/L aqueous solution of sodium hydroxide was used assaponification liquid. This saponification liquid was heated to 60° C.,and the cellulose acylate film was immersed for two minutes. Next, thecellulose acylate film was immersed in a 0.05 mol/L aqueous solution ofsulfuric acid for 30 seconds and then passed through a washing bathusing water.

(2) Production of a Polarizing Layer

According to Example 1 described in JP-A-2001-141926, the celluloseacylate film was passed through two pairs of nip rolls with differentrim speeds to stretch the film longitudinally, and thus a polarizinglayer having a thickness to 20 μm was produced.

(3) Lamination and Evaluation

The polarizing layer thus obtained and two sheets selected from theunstretched and stretched cellulose acylate films saponified in such amanner as described above were adhered such that the polarizing layerwas interposed between the cellulose acylate films and then the filmswere adhered using a 3% aqueous solution of PVA (PVA-117H, manufacturedby KURARAY Co. Ltd. as an adhesive agent so that the polarizing axis andthe longitudinal direction of the cellulose acylate films met at 90°.Among these, the unstretched and stretched cellulose acylate films weremounted on a 20-in VA type liquid crystal display device described inFIG. 2-9 in JP-A-2000-154261 at 25° C. and relative humidity of 60%, andthis was provided at 25° C. and relative humidity of 10%. By using thecellulose acylate film that was produced using the production methodaccording to the aspect of the invention, acceptable performance withsmall color tone change and less display unevenness could be obtained.

Further, when a polarizing plate was produced by using the celluloseacylate film of the invention in the same manner as in the polarizingplate stretched according to Example 1 of JP-A-2002-86554, using atenter so that the axis of stretching was inclined 45°, acceptableresults could be obtained as in the above.

(Production and Evaluation of an Optical Compensation Film)

Instead of the cellulose acetate film coated with the liquid crystallayer of Example 1 of JP-A-1999-316378, the stretched cellulose acylatefilms according to the aspect of the invention which had been subjectedto saponification were mounted on the bend-aligned liquid crystal celldescribed in Example 9 of JP-A-2002-62431 at 25° C. and a relativehumidity of 60%, and this was provided to 25° C. and a relative humidityof 10%. By using the cellulose acylate film that was obtained using theproduction method according to the aspect of the invention, acceptabledisplay performance with small light leakage and contrast change couldbe obtained.

Moreover, an optical compensation filter film was produced using thestretched cellulose acylate film, instead of the cellulose acetate filmcoated with a liquid crystal layer of Example 1 of JP-A-1995-333433. Inthis case, acceptable optical compensation film could be obtained.

Further, the polarizing plate and the phase difference polarizing plateemploying the cellulose acylate films that was produced using theproduction method according to the aspect of the invention were used inthe liquid display device described in Example 1 of JP-A-1998-48420, theoptically anisotropic layer containing discotic liquid crystal moleculesand the alignment film coated with polyvinyl alcohol described inExample 1 of JP-A-1997-26572, the 20-in VA type liquid crystal displaydevice shown in FIGS. 2 to 9 of JP-A-2000-154261, the 20-in OCB typeliquid crystal display device shown in FIGS. 10 to 15 ofJP-A-2000-154261, and the IPS type liquid crystal display device shownin FIG. 11 of JP-A-2004-12731. In this connection, acceptable liquidcrystal display devices having very small light leakage were obtained.Meanwhile, in the case of when a liquid crystal display device that wasproduced using cellulose acylate C-1 by a method other than theproduction method according to the aspect of the invention was subjectedto black displaying in a dark space, light leakage was observed.

(Production and Evaluation of a Low Reflection Film)

A low reflection film was produced by using the above-describedstretched cellulose acylate film according to Example 47 of the Journalof Technical Disclosure of the Japan Institute of Invention andInnovation (Article No. 2001-1745, published on Mar. 15, 2001, JapanInstitute of Invention and Innovation), and acceptable opticalperformance could be obtained by using the cellulose acylate film thatwas produced using the production method according to the aspect of theinvention.

Further, the above-mentioned low reflection film was attached to theoutermost layers of the liquid crystal display device described inExample 1 of JP-A-1998-48420, the 20-in VA type liquid crystal displaydevice described in FIGS. 2 to 9 of JP-A-2000-154261, the 20-in OCB typeliquid crystal display device described in FIGS. 10 to 15 ofJP-A-2000-154261, and the IPS type liquid crystal display devicedescribed in FIG. 11 of JP-A-2004-12731, and evaluation was carried out.As a result, acceptable liquid crystal display devices in whichinsignificant light leakage occurs were obtained.

INDUSTRIAL APPLICABILITY

According to the invention, cellulose acylate which is capable of beingdesirably used as an optical film and has the very small amount ofimpurity is produced. Furthermore, the optical film containing celluloseacylate is used to obtain a high grade retardation film, polarizingplate, optical compensation film, anti-reflection film, and imagedisplay device. Therefore, the invention is a useful invention with highindustrial applicability.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

The present disclosure relates to the subject matter contained inJapanese Patent Application No. 178685/2006 filed on Jun. 28, 2006 andJapanese Patent Application No. 224372/2006 filed on Aug. 21, 2006,which are expressly incorporated herein by reference in their entirety.All the publications referred to in the present specification are alsoexpressly incorporated herein by reference in their entirety.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description, and is notintended to be exhaustive or to limit the invention to the precise formdisclosed. The description was selected to best explain the principlesof the invention and their practical application to enable othersskilled in the art to best utilize the invention in various embodimentsand various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention not belimited by the specification, but be defined claims set forth below.

1. A method for producing a cellulose acylate composition, whichcomprises filtering a solution in which cellulose acylate satisfying thefollowing formulae 1 to 3 and having melt viscosity of 150 to 1000 Pasat 230° C. is dissolved in a solvent through a filter having a retentionparticle size of 0.1 to 40 μm, and mixing the filtered solution with apoor solvent to reprecipitate cellulose acylate:1.5.≦A+B≦3  Formula 10≦A≦2.0  Formula 21.0≦B≦3  Formula 3 where A is a substitution degree for an acetyl groupof a hydrogen atom which constitutes a hydroxyl group of cellulose, andB is a substitution degree for an acyl group having 3 to 7 carbon atomsof a hydrogen atom which constitutes a hydroxyl group of cellulose. 2.The method for producing the cellulose acylate composition according toclaim 1, wherein the cellulose acylate used in the solution has a weightaverage molecular weight measured by a gel permeation chromatography of80,000 to 180,000.
 3. The method for producing the cellulose acylatecomposition according to claim 1, wherein the filter has a retentionparticle size of 2 to 20 μm.
 4. The method for producing the celluloseacylate composition according to claim 1, wherein a filter aid is usedduring the filtering.
 5. The method for producing the cellulose acylatecomposition according to claim 1, wherein the reprecipitated celluloseacylate comprises 10 pieces or less of impurity particles having aparticle size of 40 μm or more per 100 g of the cellulose acylate. 6.The method for producing the cellulose acylate composition according toclaim 1, wherein the reprecipitated cellulose acylate comprises 5 piecesor less of impurity particles having a particle size of 40 μm or moreper 100 g of the cellulose acylate.
 7. The method for producing thecellulose acylate composition according to claim 1, wherein thecellulose acylate composition is in the form of a solution, a melt, agel, a pellet, or a film.
 8. The method for producing the celluloseacylate composition according to claim 1, wherein the cellulose acylatecomposition is in the form of a pellet or a film.